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Vaccination is the administration of a
vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
to help the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such ...
develop immunity from a disease. Vaccines contain a
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
or
virus A virus is a wikt:submicroscopic, submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and ...
in a weakened, live or killed state, or
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabo ...
s or
toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1 ...
s from the organism. In stimulating the body's
adaptive immunity The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system ...
, they help prevent sickness from an
infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
. When a sufficiently large percentage of a population has been vaccinated,
herd immunity Herd immunity (also called herd effect, community immunity, population immunity, or mass immunity) is a form of indirect protection that applies only to contagious diseases. It occurs when a sufficient percentage of a population has become Imm ...
results. Herd immunity protects those who may be immunocompromised and cannot get a vaccine because even a weakened version would harm them. The effectiveness of vaccination has been widely studied and verified. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of
smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The Ali Maow Maalin#Maalin's case, last naturally occurring case was diagnosed in October 1977, and the World ...
and the elimination of diseases such as
polio Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe sym ...
and
tetanus Tetanus, also known as lockjaw, is a bacterial infection caused by '' Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usual ...
from much of the world. However, some diseases, such as measles outbreaks in America, have seen rising cases due to relatively low vaccination rates in the 2010s – attributed, in part, to
vaccine hesitancy Vaccine hesitancy is a delay in acceptance, or refusal, of vaccines despite the availability of vaccine services and supporting evidence. The term covers refusals to vaccinate, delaying vaccines, accepting vaccines but remaining uncertain abou ...
. According to the
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainme ...
, vaccination prevents 3.5–5 million deaths per year. The first disease people tried to prevent by
inoculation Inoculation is the act of implanting a pathogen or other microorganism. It may refer to methods of artificial induction of immunity, artificially inducing immunity against various infectious diseases, or it may be used to describe the spreading ...
was most likely smallpox, with the first recorded use of
variolation Variolation was the method of inoculation first used to immunize individuals against smallpox (''Variola'') with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. Var ...
occurring in the 16th century in China. It was also the first disease for which a vaccine was produced. Although at least six people had used the same principles years earlier, the
smallpox vaccine The smallpox vaccine is the first vaccine to be developed against a contagious disease. In 1796, British physician Edward Jenner demonstrated that an infection with the relatively mild cowpox virus conferred immunity against the deadly smallpox ...
was invented in 1796 by English physician
Edward Jenner Edward Jenner, (17 May 1749 – 26 January 1823) was a British physician and scientist who pioneered the concept of vaccines, and created the smallpox vaccine, the world's first vaccine. The terms ''vaccine'' and ''vaccination'' are derived f ...
. He was the first to publish evidence that it was effective and to provide advice on its production.
Louis Pasteur Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation and pasteurization, the latter of which wa ...
furthered the concept through his work in microbiology. The
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ...
was called ''vaccination'' because it was derived from a virus affecting cows ( la, vacca 'cow'). Smallpox was a contagious and deadly disease, causing the deaths of 20–60% of infected adults and over 80% of infected children. When smallpox was finally eradicated in 1979, it had already killed an estimated 300–500 million people in the 20th century. ''Vaccination'' and ''
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ...
'' have a similar meaning in everyday language. This is distinct from inoculation, which uses unweakened live pathogens. Vaccination efforts have been met with some reluctance on scientific, ethical, political, medical safety, and religious grounds, although no major religions oppose vaccination, and some consider it an obligation due to the potential to save lives. In the United States, people may receive compensation for alleged injuries under the National Vaccine Injury Compensation Program. Early success brought widespread acceptance, and mass vaccination campaigns have greatly reduced the incidence of many diseases in numerous geographic regions. The
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency, under the United S ...
lists vaccination as one of the ten great public health achievements of the 20th century in the U.S.


Mechanism of function

Vaccines are a way of artificially activating the immune system to protect against
infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
. The activation occurs through priming the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such ...
with an immunogen. Stimulating immune responses with an infectious agent is known as ''
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ...
''. Vaccination includes various ways of administering immunogens. Most vaccines are administered before a patient has contracted a disease to help increase future protection. However, some vaccines are administered after the patient already has contracted a disease. Vaccines given after exposure to smallpox are reported to offer some protection from disease or may reduce the severity of disease. The first
rabies Rabies is a viral disease that causes encephalitis Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, a ...
immunization was given by
Louis Pasteur Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation and pasteurization, the latter of which wa ...
to a child after he was bitten by a rabid dog. Since its discovery, the rabies vaccine has been proven effective in preventing rabies in humans when administered several times over 14 days along with rabies immune globulin and wound care. Other examples include experimental AIDS, cancer and
Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
vaccines. Such immunizations aim to trigger an immune response more rapidly and with less harm than natural infection. Most vaccines are given by injection as they are not absorbed reliably through the
intestines The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
. Live attenuated polio, rotavirus, some typhoid, and some cholera vaccines are given orally to produce immunity in the bowel. While vaccination provides a lasting effect, it usually takes several weeks to develop. This differs from passive immunity (the transfer of
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform ...
, such as in breastfeeding), which has immediate effect. A vaccine failure is when an
organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...
contracts a disease in spite of being vaccinated against it. Primary
vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
failure occurs when an organism's immune system does not produce
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform ...
when first vaccinated. Vaccines can fail when several series are given and fail to produce an immune response. The term "vaccine failure" does not necessarily imply that the vaccine is defective. Most vaccine failures are simply from individual variations in immune response.


Vaccination versus inoculation

The term "
inoculation Inoculation is the act of implanting a pathogen or other microorganism. It may refer to methods of artificial induction of immunity, artificially inducing immunity against various infectious diseases, or it may be used to describe the spreading ...
" is often used interchangeably with "vaccination." However, while related, the terms are not synonymous. Vaccination is treatment of an individual with an attenuated (i.e. less virulent)
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ ...
or other immunogen, whereas inoculation, also called
variolation Variolation was the method of inoculation first used to immunize individuals against smallpox (''Variola'') with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. Var ...
in the context of
smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The Ali Maow Maalin#Maalin's case, last naturally occurring case was diagnosed in October 1977, and the World ...
prophylaxis, is treatment with unattenuated variola virus taken from a pustule or scab of a smallpox patient into the superficial layers of the skin, commonly the upper arm. Variolation was often done 'arm-to-arm' or, less effectively, 'scab-to-arm', and often caused the patient to become infected with smallpox, which in some cases resulted in severe disease. Vaccinations began in the late 18th century with the work of
Edward Jenner Edward Jenner, (17 May 1749 – 26 January 1823) was a British physician and scientist who pioneered the concept of vaccines, and created the smallpox vaccine, the world's first vaccine. The terms ''vaccine'' and ''vaccination'' are derived f ...
and the smallpox vaccine.


Preventing disease versus preventing infection

Some vaccines, like the smallpox vaccine, prevent infection. Their use results in sterilizing immunity and can help eradicate a disease if there is no animal reserve. Other vaccines, including those for , help to (temporarily) lower the chance of severe disease for individuals, without necessarily reducing the probability of becoming infected.


Safety


Vaccine development and approval

Just like any medication or procedure, no vaccine can be 100% safe or effective for everyone because each person's body can react differently. While minor
side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s, such as soreness or low grade fever, are relatively common, serious side effects are very rare and occur in about 1 out of every 100,000 vaccinations and typically involve
allergic reactions Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune ...
that can cause hives or difficulty breathing. However, vaccines are the safest they ever have been in history and each vaccine undergoes rigorous clinical trials to ensure their safety and
efficacy Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as ''effectiveness Effectiveness is the capability of producing a desired result or the ability to produce desired output. Wh ...
before approval by authorities such as the US
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA). Prior to human testing, vaccines are tested on
cell culture Cell culture or tissue culture is the process by which cell (biology), cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas B ...
s and the results modelled to assess how they will interact with the immune system. During the next round of testing, researchers study vaccines in animals, including
mice A mouse (plural, : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus mus ...
,
rabbit Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family (biology), family Leporidae (which also contains the hares) of the order (biology), order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' i ...
s,
guinea pig The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus ''Cavia'' in the family Caviidae. Animal fancy, Breeders tend to use the word ''cavy'' to de ...
s, and
monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...
s. Vaccines that pass each of these stages of testing are then approved by the public health safety authority (FDA in the United States) to start a three-phase series of human testing, advancing to higher phases only if they are deemed safe and effective at the previous phase. The people in these trials participate voluntarily and are required to prove they understand the purpose of the study and the potential risks. During phase I trials, a vaccine is tested in a group of about 20 people with the primary goal of assessing the vaccine's safety. Phase II trials expand the testing to include 50 to several hundred people. During this stage, the vaccine's safety continues to be evaluated and researchers also gather data on the effectiveness and the ideal dose of the vaccine. Vaccines determined to be safe and efficacious then advance to phase III trials, which focuses on the efficacy of the vaccine in hundreds to thousands of volunteers. This phase can take several years to complete and researchers use this opportunity to compare the vaccinated volunteers to those who have not been vaccinated to highlight any true reactions to the vaccine that occur. If a vaccine passes all of the phases of testing, the manufacturer can then apply for license of the vaccine through the FDA. Before the FDA approves use in the general public, they extensively review the results to the clinical trials, safety tests, purity tests, and manufacturing methods and establish that the manufacturer itself is up to government standards in many other areas. However, safety testing of the vaccines never ends. After FDA approval, the FDA continues to monitor the manufacturing protocols, batch purity, and the manufacturing facility itself. Additionally, most vaccines also undergo phase IV trials, which monitors the safety and efficacy of vaccines in tens of thousands of people, or more, across many years. This allows for delayed or very rare reactions to be detected and evaluated.


Side effects

The
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency, under the United S ...
(CDC) has compiled a list of vaccines and their possible side effects. The risk of side effects varies from one vaccine to the next, but below are examples of side effects and their approximate rate of occurrence with the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine, a common childhood vaccine. Mild side effects (common) * Mild fever (1 in 4) * Redness, soreness, swelling at the injection site (1 in 4) * Fatigue, poor appetite (1 in 10) * Vomiting (1 in 50) Moderate side effects (uncommon) * Seizure (1 in 14,000) * High fever (over 105 °F) (1 in 16,000) Severe side effects (rare) * Serious allergic reaction (1 in 1,000,000) * Other severe problems including long-term seizure, coma, brain damage have been reported, but are so rare that it is not possible to tell if they are from the vaccine or not. Certain vaccines have had adverse outcomes identified after being used in mass vaccination programs: **In 1976 in the United States, a mass a swine flu vaccination programme was discontinued after 362 cases of
Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness Muscle weakness is a lack of muscle strength. Its causes are many and can be divided into conditions that have either true or perceived muscle weakness. True muscle weakness ...
among 45 million vaccinated people. William Foege of the CDC estimated that the incidence of Guillain-Barré was four times higher in vaccinated people than in those not receiving the swine flu vaccine. ** Dengvaxia, the only approved vaccine for
Dengue fever Dengue fever is a mosquito-borne tropical disease caused by the dengue virus ''Dengue virus'' (DENV) is the cause of dengue fever. It is a mosquito-borne, single positive-stranded RNA virus of the family ''Flaviviridae''; genus ''Flavivi ...
, was found to increase the risk of hospitalization for Dengue fever by 1.58 times in children of 9 years or younger, resulting in the suspension of a mass vaccination program in the Philippines in 2017. ** Pandemrix a vaccine for the
H1N1 In virology, influenza A virus subtype H1N1 (A/H1N1) is a subtype of influenza A virus. Major outbreaks of H1N1 strains in humans include the Spanish flu, the 1977 Russian flu, 1977 Russian flu pandemic and the 2009 swine flu pandemic. It is a ...
pandemic of 2009 given to around 31 million people was found to have a higher level of adverse events than alternative vaccines resulting in legal action. In a response to the
narcolepsy Narcolepsy is a Chronic condition, long-term neurological disorder that involves a decreased ability to regulate circadian rhythm, sleep–wake cycles. Symptoms often include periods of excessive daytime sleepiness and brief involuntary sleep ...
reports following immunization with Pandemrix, the CDC carried out a population-based study and found the FDA-approved 2009 H1N1 flu shots were not associated with an increased risk for the neurological disorder.


Ingredients

The ingredients of vaccines can vary greatly from one to the next and no two vaccines are the same. The CDC has compiled a list of vaccines and their ingredients that is readily accessible on their website.


Aluminium

Aluminium Aluminium (aluminum in American and Canadian English) is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substan ...
is an adjuvant ingredient in some vaccines. An adjuvant is a type of ingredient that is used to help the body's immune system create a stronger immune response after receiving the vaccination. Aluminium is in a
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in the form of a natural crystallinity, crystalline mineral is known as rock salt or halite. ...
form (the ionic version of an element) and is used in the following compounds:
aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is Amphoter ...
,
aluminium phosphate Aluminium phosphate is a chemical compound. In nature it occurs as the mineral berlinite. Many synthetic forms of aluminium phosphate are known. They have framework structures similar to zeolites and some are used as catalysts, ion-exchangers or ...
, and
aluminium potassium sulfate Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the double sulfate of potassium and aluminium, with chemical formula KAl(SO4)2. It is commonly encountered as the hydrate, dodecahydrate, KAl(SO4)2·12H2O. It c ...
. For a given element, the ion form has different properties from the elemental form. Although it is possible to have aluminium toxicity, aluminium salts have been used effectively and safely since the 1930s when they were first used with the
diphtheria Diphtheria is an infection caused by the bacteria, bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild Course (medicine), clinical course, but in some outbreaks more than 10% of those diagnosed with the di ...
and
tetanus Tetanus, also known as lockjaw, is a bacterial infection caused by '' Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usual ...
vaccines. Although there is a small increase in the chance of having a local reaction to a vaccine with an aluminium salt (redness, soreness, and swelling), there is no increased risk of any serious reactions.


Mercury

Certain vaccines once contained a compound called thiomersal or thimerosal, which is an
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other carbon atoms), millions of organic c ...
containing mercury.
Organomercury Organomercury refers to the group of Organometallic chemistry, organometallic compounds that contain mercury (element), mercury. Typically the Hg–C bond is stable toward air and moisture but sensitive to light. Important organomercury compounds a ...
is commonly found in two forms. The
methylmercury Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a ...
cation (with one carbon atom) is found in mercury-contaminated fish and is the form that people might ingest in mercury-polluted areas (
Minamata disease Minamata disease is a neurological disease caused by severe mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may includ ...
), whereas the ethylmercury cation (with two carbon atoms) is present in thimerosal, linked to thiosalicylate. Although both are organomercury compounds, they do not have the same chemical properties and interact with the human body differently. Ethylmercury is cleared from the body faster than methylmercury and is less likely to cause toxic effects. Thimerosal was used as a
preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by ...
to prevent the growth of
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometre The micrometre (Amer ...
and
fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
in vials that contain more than one dose of a vaccine. This helps reduce the risk of potential
infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
s or serious illness that could occur from
contamination Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, wiktionary:Workplace, workplace, etc. Typ ...
of a vaccine vial. Although there was a small increase in risk of injection site redness and swelling with vaccines containing thimerosal, there was no increased risk of serious harm or
autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder, neurodevelopmental condition (or conditions) ...
. Even though evidence supports the safety and efficacy of thimerosal in vaccines, thimerosal was removed from childhood vaccines in the United States in 2001 as a precaution.


Monitoring

The administration protocols, efficacy, and adverse events of vaccines are monitored by organizations of the US federal government, including the CDC and FDA, and independent agencies are constantly re-evaluating vaccine practices. As with all medications, vaccine use is determined by
public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...
research, surveillance, and reporting to governments and the public.


Usage

The
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainme ...
(WHO) has estimated that vaccination prevents 3.5–5 million deaths per year, and up to 1.5 million children die each year due to diseases that could have been prevented by vaccination. They estimate that 29% of deaths of children under five-years-old in 2013 were vaccine preventable. In other developing parts of the world, they are faced with the challenge of having a decreased availability of resources and vaccinations. Countries such as those in
Sub-Saharan Africa Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
cannot afford to provide the full range of childhood vaccinations.


United States

Vaccines have led to major decreases in the prevalence of infectious diseases in the United States. In 2007, studies regarding the effectiveness of vaccines on mortality or morbidity rates of those exposed to various diseases have shown almost 100% decreases in death rates, and about a 90% decrease in exposure rates. This has allowed specific organizations and states to adopt standards for recommended early childhood vaccinations. Lower income families who are unable to otherwise afford vaccinations are supported by these organizations and specific government laws. The Vaccines for Children Program and the
Social Security Act The Social Security Act of 1935 is a law enacted by the 74th United States Congress and signed into law by US President Franklin D. Roosevelt. The law created the Social Security (United States), Social Security program as well as insurance aga ...
are two major players in supporting lower socioeconomic groups. In 2000, the CDC declared that measles had been eliminated in the US (defined as no disease transmission for 12 continuous months). However, with the growing anti-vaccine movement, the US has seen a resurgence of certain
vaccine-preventable diseases A vaccine-preventable disease is an infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they pr ...
. The measles virus has now lost its elimination status in the US as the number of measles cases continues to rise in recent years with a total of 17 outbreaks in 2018 and 465 outbreaks in 2019 (as of 4 April 2019).


History

Before the first vaccinations, in the sense of using
cowpox Cowpox is an infectious disease caused by the ''cowpox virus'' (CPXV). It presents with large vesicle (dermatology), blisters in the skin, a fever and lymphadenopathy, swollen glands, historically typically following contact with an infected cow, ...
to inoculate people against
smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The Ali Maow Maalin#Maalin's case, last naturally occurring case was diagnosed in October 1977, and the World ...
, people have been inoculated in China and elsewhere, before being copied in the west, by using smallpox, called
variolation Variolation was the method of inoculation first used to immunize individuals against smallpox (''Variola'') with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. Var ...
. The earliest hints of the practice of variolation for smallpox in China come during the 10th century. The Chinese also practiced the oldest documented use of variolation, which comes from Wan Quan's (1499–1582) Douzhen Xinfa (痘疹心法) of 1549. They implemented a method of "nasal insufflation" administered by blowing powdered smallpox material, usually scabs, up the nostrils. Various insufflation techniques have been recorded throughout the sixteenth and seventeenth centuries within China. Two reports on the Chinese practice of
inoculation Inoculation is the act of implanting a pathogen or other microorganism. It may refer to methods of artificial induction of immunity, artificially inducing immunity against various infectious diseases, or it may be used to describe the spreading ...
were received by the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, ...
in London in 1700; one by
Martin Lister Martin Lister FRS (12 April 1639 – 2 February 1712) was an English naturalist and physician. His daughters Anne and Susanna were two of his illustrators and engravers. J. D. Woodley, ‘Lister , Susanna (bap. 1670, d. 1738)’, Oxford Dic ...
who received a report by an employee of the
East India Company The East India Company (EIC) was an English, and later British, joint-stock company founded in 1600 and dissolved in 1874. It was formed to Indian Ocean trade, trade in the Indian Ocean region, initially with the East Indies (the Indian subco ...
stationed in China and another by
Clopton Havers Clopton Havers (24 February 1657 – April 1702) was an English physician A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply doctor, is a hea ...
. In France,
Voltaire François-Marie Arouet (; 21 November 169430 May 1778) was a French Age of Enlightenment, Enlightenment writer, historian, and philosopher. Known by his ''Pen name, nom de plume'' M. de Voltaire (; also ; ), he was famous for his wit, and his ...
reports that the Chinese have practiced variolation "these hundred years". In 1796,
Edward Jenner Edward Jenner, (17 May 1749 – 26 January 1823) was a British physician and scientist who pioneered the concept of vaccines, and created the smallpox vaccine, the world's first vaccine. The terms ''vaccine'' and ''vaccination'' are derived f ...
, a doctor in Berkeley in
Gloucestershire Gloucestershire ( abbreviated Glos) is a Counties of England, county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn and the entire Forest of Dean. The county town ...
, England, tested a common theory that a person who had contracted cowpox would be immune from smallpox. To test the theory, he took cowpox
vesicle Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...
s from a milkmaid named Sarah Nelmes with which he infected an eight-year-old boy named James Phipps, and two months later he inoculated the boy with smallpox, and smallpox did not develop. In 1798, Jenner published '' An Inquiry Into the Causes and Effects of the Variolæ Vaccinæ'' which created widespread interest. He distinguished 'true' and 'spurious' cowpox (which did not give the desired effect) and developed an "arm-to-arm" method of propagating the vaccine from the vaccinated individual's
pustule A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of ...
. Early attempts at confirmation were confounded by contamination with smallpox, but despite controversy within the medical profession and religious opposition to the use of animal material, by 1801 his report was translated into six languages and over 100,000 people were vaccinated. The term ''vaccination'' was coined in 1800 by the surgeon Richard Dunning in his text ''Some observations on vaccination''. In 1802, the Scottish physician Helenus Scott vaccinated dozens of children in
Bombay Mumbai (, ; also known as Bombay — List of renamed Indian cities and states#Maharashtra, the official name until 1995) is the capital city of the Indian States and union territories of India, state of Maharashtra and the ''de facto'' fin ...
against smallpox using Jenner's cowpox vaccine. In the same year Scott penned a letter to the editor in the '' Bombay Courier'', declaring that "We have it now in our power to communicate the benefits of this important discovery to every part of India, perhaps to China and the whole eastern world". Subsequently, vaccination became firmly established in
British India The provinces of India, earlier presidencies of British India and still earlier, presidency towns, were the administrative divisions of British governance on the Indian subcontinent. Collectively, they have been called British India. In one ...
. A vaccination campaign was started in the new British colony of
Ceylon Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...
in 1803. By 1807 the British had vaccinated more than a million Indians and Sri Lankans against smallpox. Also in 1803 the Spanish Balmis Expedition launched the first transcontinental effort to vaccinate people against smallpox. Following a smallpox epidemic in 1816 the
Kingdom of Nepal The Kingdom of Nepal ( ne, नेपाल अधिराज्य), also known as the Gorkha Empire ( ne, गोरखा अधिराज्य) or Asal Hindustan ( ne, असल हिन्दुस्तान)(), was a Hindu king ...
ordered smallpox vaccine and requested the English veterinarian William Moorcroft to help in launching a vaccination campaign. In the same year a law was passed in Sweden to require the vaccination of children against smallpox by the age of two.
Prussia Prussia, , Old Prussian: ''Prūsa'' or ''Prūsija'' was a Germans, German state on the southeast coast of the Baltic Sea. It formed the German Empire under Prussian rule when it united the German states in 1871. It was ''de facto'' dissolved ...
briefly introduced compulsory vaccination in 1810 and again in the 1920s, but decided against a compulsory vaccination law in 1829. A law on compulsory smallpox vaccination was introduced in the
Province of Hanover The Province of Hanover (german: Provinz Hannover) was a Provinces of Prussia, province of the Kingdom of Prussia and the Free State of Prussia from 1868 to 1946. During the Austro-Prussian War, the Kingdom of Hanover had attempted to maintain ...
in the 1820s. In 1826, in
Kragujevac Kragujevac ( sr-Cyrl, Крагујевац, ) is the List of cities in Serbia, fourth largest city in Serbia and the administrative centre of the Šumadija District. It is the historical centre of the geographical region of Šumadija in central Se ...
, future prince Mihailo of
Serbia Serbia (, ; Serbian language, Serbian: , , ), officially the Republic of Serbia (Serbian language, Serbian: , , ), is a landlocked country in Southeast Europe, Southeastern and Central Europe, situated at the crossroads of the Pannonian Bas ...
was the first person to be vaccinated against smallpox in the principality of Serbia. Following a smallpox epidemic in 1837 that caused 40,000 deaths, the
British government ga, Rialtas a Shoilse gd, Riaghaltas a Mhòrachd , image = HM Government logo.svg , image_size = 220px , image2 = Royal Coat of Arms of the United Kingdom (HM Government).svg , image_size2 = 180px , caption = Royal coat of arms of t ...
initiated a concentrated vaccination policy, starting with the Vaccination Act of 1840, which provided for universal vaccination and prohibited
variolation Variolation was the method of inoculation first used to immunize individuals against smallpox (''Variola'') with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. Var ...
. The Vaccination Act 1853 introduced compulsory smallpox vaccination in England and Wales. The law followed a severe outbreak of smallpox in 1851 and 1852. It provided that the
poor law In Kingdom of England, English and British Isles, British history, poor relief refers to government and ecclesiastical action to relieve poverty. Over the centuries, various authorities have needed to decide whose poverty deserves relief and a ...
authorities would continue to dispense vaccination to all free of charge, but that records were to be kept on vaccinated children by the network of births registrars. It was accepted at the time, that voluntary vaccination had not reduced smallpox mortality, but the Vaccination Act 1853 was so badly implemented that it had little impact on the number of children vaccinated in England and
Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
. The U.S. Supreme Court upheld compulsory vaccination laws in the 1905 landmark case Jacobson v. Massachusetts, ruling that laws could require vaccination to protect the public from dangerous communicable diseases. However, in practice the U.S. had the lowest rate of vaccination among industrialized nations in the early 20th century. Compulsory vaccination laws began to be enforced in the U.S. after
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. In 1959, the WHO called for the eradication of smallpox worldwide, as smallpox was still endemic in 33 countries. In the 1960s six to eight children died each year in the U.S. from vaccination-related complications. According to the WHO there were in 1966 about 100 million cases of smallpox worldwide, causing an estimated two million deaths. In the 1970s there was such a small risk of contracting smallpox that the U.S. Public Health Service recommended for routine smallpox vaccination to be ended. By 1974 the WHO smallpox vaccination program had confined smallpox to parts of
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
, India,
Bangladesh Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world, with a population exceeding 165 million pe ...
,
Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
and
Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constitut ...
. In 1977 the WHO recorded the last case of smallpox infection acquired outside a laboratory in Somalia. In 1980 the WHO officially declared the world free of smallpox. In 1974 the WHO adopted the goal of universal vaccination by 1990 to protect children against six preventable infectious diseases:
measles Measles is a highly contagious infectious disease caused by Measles morbillivirus, measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often ...
,
poliomyelitis Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe sym ...
,
diphtheria Diphtheria is an infection caused by the bacteria, bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild Course (medicine), clinical course, but in some outbreaks more than 10% of those diagnosed with the di ...
,
whooping cough Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold The common cold or the cold is a virus, viral infectious disease of ...
,
tetanus Tetanus, also known as lockjaw, is a bacterial infection caused by '' Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usual ...
, and
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
. In the 1980s only 20 to 40% of children in developing countries were vaccinated against these six diseases. In wealthy nations the number of measles cases had dropped dramatically after the introduction of the
measles vaccine Measles vaccine protects against becoming infected with measles. Nearly all of those who do not develop immunity after a single dose develop it after a second dose. When rate of vaccination within a population is greater than 92%, Disease outbre ...
in 1963. WHO figures demonstrate that in many countries a decline in measles vaccination leads to a resurgence in measles cases. Measles are so contagious that public health experts believe a vaccination rate of 100% is needed to control the disease. Despite decades of mass vaccination polio remains a threat in India,
Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of G ...
,
Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constitut ...
,
Niger ) , official_languages = , languages_type = National languagesAfghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...
, Bangladesh and
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. It consists of over List of islands of Indonesia, 17,000 islands, including Sumatr ...
. By 2006 global health experts concluded that the eradication of polio was only possible if the supply of
drinking water Drinking water is water that is used in drinking, drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity ...
and
sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of Human waste, human excreta and sewage. Risk management, Preventing human contact with feces is part of sanitation, as is hand washing wi ...
facilities were improved in
slums A slum is a highly populated Urban area, urban residential area consisting of densely packed housing units of weak build quality and often associated with poverty. The infrastructure in slums is often deteriorated or incomplete, and they are p ...
. The deployment of a combined DPT vaccine against
diphtheria Diphtheria is an infection caused by the bacteria, bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild Course (medicine), clinical course, but in some outbreaks more than 10% of those diagnosed with the di ...
,
pertussis Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two o ...
(whooping cough), and
tetanus Tetanus, also known as lockjaw, is a bacterial infection caused by '' Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usual ...
in the 1950s was considered a major advancement for public health. But in the course of vaccination campaigns that spanned decades, DPT vaccines became associated with high incidences of side effects. Despite improved DPT vaccines coming onto the market in the 1990s DPT vaccines became the focus of anti-vaccination campaigns in wealthy nations. As immunization rates fell outbreaks of
pertussis Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two o ...
increased in many countries. In 2000, the Global Alliance for Vaccines and Immunization was established to strengthen routine vaccinations and introduce new and underused vaccines in countries with a per capita GDP of under US$1000.


Vaccination policy

To eliminate the risk of
outbreaks In epidemiology, an outbreak is a sudden increase in occurrences of a disease when cases are in excess of normal expectancy for the location or season. It may affect a small and localized group or impact upon thousands of people across an entire ...
of some diseases, at various times governments and other institutions have employed policies requiring vaccination for all people. For example, an 1853 law required universal vaccination against smallpox in England and Wales, with fines levied on people who did not comply. Common contemporary U.S. vaccination policies require that children receive recommended vaccinations before entering public school. Beginning with early vaccination in the nineteenth century, these policies were resisted by a variety of groups, collectively called antivaccinationists, who object on scientific, ethical, political, medical safety,
religious Religion is usually defined as a social system, social-cultural system of designated religious behaviour, behaviors and practices, morality, morals, beliefs, worldviews, religious text, texts, sacred site, sanctified places, prophecy, prophecie ...
, and other grounds. Common objections are that vaccinations do not work, that compulsory vaccination constitutes excessive government intervention in personal matters, or that the proposed vaccinations are not sufficiently safe. Many modern vaccination policies allow exemptions for people who have compromised immune systems, allergies to the components used in vaccinations or strongly held objections. In countries with limited financial resources, limited vaccination coverage results in greater morbidity and mortality due to infectious disease. More affluent countries are able to subsidize vaccinations for at-risk groups, resulting in more comprehensive and effective coverage. In Australia, for example, the Government subsidizes vaccinations for seniors and indigenous Australians. Public Health Law Research, an independent US based organization, reported in 2009 that there is insufficient evidence to assess the effectiveness of requiring vaccinations as a condition for specified jobs as a means of reducing incidence of specific diseases among particularly vulnerable populations; that there is sufficient evidence supporting the effectiveness of requiring vaccinations as a condition for attending child care facilities and schools; and that there is strong evidence supporting the effectiveness of standing orders, which allow healthcare workers without prescription authority to administer vaccine as a public health intervention.


Fractional dose vaccination

Fractional dose vaccination reduces the dose of a vaccine to allow more individuals to be vaccinated with a given vaccine stock, trading societal benefit for individual protection. Based on the
nonlinearity In mathematics and science, a nonlinear system is a system in which the change of the output is not proportionality (mathematics), proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, m ...
properties of many vaccines, it is effective in poverty diseases and promises benefits in pandemic waves, e.g. in
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
, when vaccine supply is limited.


Litigation

Allegations of vaccine injuries in recent decades have appeared in litigation in the U.S. Some families have won substantial awards from sympathetic juries, even though most
public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...
officials have said that the claims of injuries were unfounded. In response, several vaccine makers stopped production, which the US government believed could be a threat to
public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...
, so laws were passed to shield manufacturers from liabilities stemming from vaccine injury claims. The safety and side effects of multiple vaccines have been tested to uphold the viability of vaccines as a barrier against disease. The
influenza vaccine Influenza vaccines, also known as flu shots, are vaccines that protect against infection by influenza viruses. New versions of the vaccines are developed twice a year, as the influenza virus rapidly changes. While their effectiveness varies fro ...
was tested in controlled trials and proven to have negligible side effects equal to that of a placebo. Some concerns from families might have arisen from social beliefs and norms that cause them to Vaccine hesitancy, mistrust or refuse vaccinations, contributing to this discrepancy in side effects that were unfounded.


Opposition

Opposition to vaccination, from a wide array of vaccine critics, has existed since the earliest vaccination campaigns. It is widely accepted that the benefits of preventing serious illness and death from
infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
s greatly outweigh the risks of rare serious adverse effect (medicine), adverse effects following
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ...
. Some studies have claimed to show that current vaccine schedules increase infant mortality and hospitalization rates; those studies, however, are correlational in nature and therefore cannot demonstrate causal effects, and the studies have also been criticized for cherry picking the comparisons they report, for ignoring historical trends that support an opposing conclusion, and for counting vaccines in a manner that is "completely arbitrary and riddled with mistakes".Gorski, David. (16 May 2011)
Vaccines and infant mortality rates
, ''Respectful Insolence''. Retrieved 28 May 2021.
Various disputes have arisen over the morality, ethics, Efficacy, effectiveness, and safety of vaccination. Some vaccination critics say that vaccines are ineffective against disease or that vaccine safety studies are inadequate. Some religious groups do not allow vaccination, and some political groups oppose mandatory vaccination on the grounds of Liberty, individual liberty. In response, concern has been raised that spreading Disinformation, unfounded information about the medical risks of vaccines increases rates of life-threatening infections, not only in the children whose parents refused vaccinations, but also in those who cannot be vaccinated due to age or immunodeficiency, who could contract infections from unvaccinated carriers (see
herd immunity Herd immunity (also called herd effect, community immunity, population immunity, or mass immunity) is a form of indirect protection that applies only to contagious diseases. It occurs when a sufficient percentage of a population has become Imm ...
). Some parents believe vaccinations cause
autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder, neurodevelopmental condition (or conditions) ...
, although there is no scientific evidence to support this idea. In 2011, Andrew Wakefield, a leading proponent of the MMR-autism myth, theory that MMR vaccine causes autism, was found to have been financially motivated to falsify research data and was subsequently stripped of his medical license. In the United States people who refuse vaccines for non-medical reasons have made up a large percentage of the cases of
measles Measles is a highly contagious infectious disease caused by Measles morbillivirus, measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often ...
, and subsequent cases of permanent hearing loss and death caused by the disease. Many parents do not vaccinate their children because they feel that diseases are no longer present due to vaccination. This is a false assumption, since diseases held in check by immunization programs can and do still return if immunization is dropped. These pathogens could possibly infect vaccinated people, due to the pathogen's ability to mutate when it is able to live in unvaccinated hosts. In 2010, California had the worst
whooping cough Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold The common cold or the cold is a virus, viral infectious disease of ...
outbreak in 50 years. A possible contributing factor was parents choosing not to vaccinate their children. There was also a case in Texas in 2012 where 21 members of a church contracted measles because they chose not to immunize.


Vaccination and autism

The notion of a connection between vaccines and autism originated in a 1998 paper published in ''The Lancet'' whose lead author was the physician Andrew Wakefield. His study concluded that eight of the 12 patients (ages 3–10) developed behavioral symptoms consistent with autism following the MMR vaccine (an immunization against
measles Measles is a highly contagious infectious disease caused by Measles morbillivirus, measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often ...
, mumps, and rubella). The article was widely criticized for lack of scientific rigor and it was proven that Wakefield falsified data in the article. In 2004, 10 of the original 12 co-authors (not including Wakefield) published a Retraction in academic publishing, retraction of the article and stated the following: "We wish to make it clear that in this paper no causal link was established between MMR vaccine and autism as the data were insufficient." In 2010, ''The Lancet'' officially retracted the article, stating that several elements of the article were incorrect, including falsified data and protocols. The article has sparked a much greater anti-vaccination movement, particularly in the United States, and even though the article was shown to be fraudulent and was heavily retracted, one in four parents still believe that vaccines can cause autism. To date, all validated and definitive studies have shown that there is no correlation between vaccines and autism. One of the studies published in 2015 confirms there is no link between MMR vaccine and autism, autism and the MMR vaccine. Infants were given a health plan, that included an MMR vaccine, and were continuously studied until they reached five years old. There was no link between the vaccine and children who had a normally developed sibling or a sibling that had autism making them a higher risk for developing autism themselves. It can be difficult to correct the memory of humans when wrong information is received prior to correct information. Even though there is much evidence to go against the Wakefield study and retractions were published by most of the co-authors, many people continue to believe and base decisions on the study as it still lingers in their memory. Studies and research are being conducted to determine effective ways to correct misinformation in the public memory. Since the Wakefield study was released over 20 years ago, it may prove easier for newer generations to be properly educated on vaccinations. A very small percentage of people have adverse reactions to vaccines, and if there is a reaction it is often mild; these reactions do not include autism.


Routes of administration

A vaccine administration may be oral, by injection (intramuscular, intradermal, subcutaneous), by puncture, transdermal or intranasal. Several recent clinical trials have aimed to deliver the vaccines via mucosal surfaces to be up-taken by the Mucosal immunology, common mucosal immunity system, thus avoiding the need for injections.


Economics of vaccination

Health is often used as one of the metrics for determining the economic prosperity of a country. This is because healthier individuals are generally better suited to contributing to the economic development of a country than the sick. There are many reasons for this. For instance, a person who is vaccinated for influenza not only protects themselves from the risk of influenza, but simultaneously also prevents themselves from infecting those around them. This leads to a healthier society, which allows individuals to be more economically productive. Children are consequently able to attend school more often and have been shown to do better academically. Similarly, adults are able to work more often, more efficiently, and more effectively.


Costs and benefits

On the whole, vaccinations induce a net benefit to society. Vaccines are often noted for their high Return on investment (ROI) values, especially when considering the long-term effects. Some vaccines have much higher ROI values than others. Studies have shown that the ratios of vaccination benefits to costs can differ substantially—from 27:1 for diphtheria/pertussis, to 13.5:1 for measles, 4.76:1 for varicella, and 0.68–1.1 : 1 for pneumococcal conjugate. Some governments choose to subsidize the costs of vaccines, due to some of the high ROI values attributed to vaccinations. The United States subsidizes over half of all vaccines for children, which costs between $400 and $600 each. Although most children do get vaccinated, the adult population of the USA is still below the recommended immunization levels. Many factors can be attributed to this issue. Many adults who have other health conditions are unable to be safely immunized, whereas others opt not to be immunized for the sake of private financial benefits. Many Americans are underinsured, and, as such, are required to pay for vaccines out-of-pocket. Others are responsible for paying high deductibles and co-pays. Although vaccinations usually induce long-term economic benefits, many governments struggle to pay the high short-term costs associated with labor and production. Consequently, many countries neglect to provide such services. According to a 2021 paper, vaccinations against Haemophilus influenzae, haemophilus influenzae type b, hepatitis B, Human papillomavirus infection, human papillomavirus, Japanese encephalitis,
measles Measles is a highly contagious infectious disease caused by Measles morbillivirus, measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often ...
, Neisseria meningitidis, neisseria meningitidis serogroup A, rotavirus, rubella, streptococcus pneumoniae, and yellow fever have prevented an estimated 50 million deaths from 2000 to 2019. The paper "represents the largest assessment of vaccine impact before COVID-19-related disruptions". According to a June 2022 study, COVID-19 vaccine, COVID19 vaccinations prevented an additional 14.4 to 19.8 million deaths in 185 countries and territories from 8 December 2020 to 8 December 2021. The Coalition for Epidemic Preparedness Innovations published a study in ''The Lancet'' in 2018 which estimated the costs of developing vaccines for diseases that could escalate into global humanitarian crises. They focused on 11 diseases which cause relatively few deaths at present and primarily strike the poor which have been highlighted as pandemic risks: *Crimean Congo hemorrhagic fever *Chikungunya *Ebola *Lassa fever *Marburg virus disease *Middle East respiratory syndrome coronavirus *Nipah virus infection *Rift Valley fever *Severe acute respiratory syndrome *Severe fever with thrombocytopenia syndrome *Zika They estimated that it would cost between $2.8 billion and $3.7 billion to develop at least one vaccine for each of them. This should be set against the potential cost of an outbreak. The 2003 SARS outbreak in East Asia cost $54 billion. Game theory uses Utility, utility functions to model costs and benefits, which may include financial and non-financial costs and benefits. In recent years, it has been argued that game theory can effectively be used to model vaccine uptake in societies. Researchers have used game theory for this purpose to analyse vaccination uptake in the context of diseases such as influenza and measles. Game theoretic analysis can be especially beneficial when a large and complex range of factors and parameters need to be taken into account by individuals in making vaccination decisions, and several options for vaccination are available, such as in the context of COVID-19 vaccination. Piraveenan et al. has argued that game theory, particularly when used in conjunction with models of bounded rationality of people, can be an effective tool in modelling and predicting COVID-19 vaccination uptake, which can in turn guide government policy.


Gallery

File:Jenner phipps 01.jpg, Dr Jenner performing his first vaccination on James Phipps, a boy of age 8. 14 May 1796. Painting by Ernest Board (early 20th century) File:The cow pock.jpg, James Gillray's ''The Cow-Pock—or—the Wonderful Effects of the New Inoculation!'', an 1802 caricature of vaccinated patients who feared it would make them sprout cowlike appendages File:Londre wellcome institute boilly vaccinee.jpg, ''La vaccine'' or ''Le préjugé vaincu'' by Louis-Léopold Boilly, 1807 File:A doctor vaccinating a small girl, other girls with loosened Wellcome V0016682.jpg, ''A doctor vaccinating a small girl, other girls with loosened blouses wait their turn apprehensively'' by Lance Calkin File:'Serum straight from the horse'., inoculation caricature Wellcome L0009827.jpg, German caricature showing Emil von Behring, von Behring extracting the serum with a tap File:The history of vaccination seen from an economic point of vi Wellcome V0011691.jpg, ''Les Malheurs de la Vaccine'' (The history of vaccination seen from an economic point of view: A pharmacy up for sale; an outmoded inoculist selling his premises; Jenner, to the left, pursues a skeleton with a lancet)


See also

* Antitoxin * Correlates of immunity * COVID-19 vaccine * DNA vaccination * Feline vaccination * H5N1 clinical trials * Immunization during pregnancy * List of vaccine topics * Misinformation related to vaccination * Vaccination and religion * Vaccination of dogs * Vaccinator * Vaccine trial * World Immunization Week


References


Further reading

* * * * *


External links


U.S. government Vaccine Research Center
Information regarding preventive vaccine research studies
The Vaccine Page
links to resources in many countries.
Immunisation schedule for the UK. Published by the UK Department of Health.
(PDF)
CDC.gov
– 'National Immunization Program: leading the way to healthy lives', Centers for Disease Control, US Centers for Disease Control (CDC information on vaccinations)
CDC.gov
– 'Mercury and Vaccines (Thimerosal)', US Centers for Disease Control

– Vaccines timeline
Immunize.org
– Immunization Action Coalition' (nonprofit working to increase immunization rates)
WHO.int
– 'Immunizations, vaccines and biologicals: Towards a World free of Vaccine Preventable Diseases',
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainme ...
(WHO's global vaccination campaign website)
Health-EU Portal
Vaccinations in the EU
History of Vaccines
Medical education site from the College of Physicians of Philadelphia, the oldest medical professional society in the US
Images of vaccine-preventable diseases

Immunisation
BBC Radio 4 discussion with Nadja Durbach, Chris Dye & Sanjoy Bhattacharya (''In Our Time'', 20 April 2006) {{Authority control Vaccination, Biotechnology