Post-exposure prophylaxis, also known as post-exposure prevention (PEP), is any preventive medical treatment started after exposure to a

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 ...

in order to prevent the infection from occurring.

COVID-19

In 2021, the

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

has approved bamlanivimab and

etesevimab Bamlanivimab/etesevimab is a combination of two monoclonal antibodies, bamlanivimab and etesevimab, administered together via intravenous infusion as a treatment for COVID-19. Both types of antibody target the surface spike protein of SAR ...

for post-exposure prophylaxis against

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 ...

Rabies

PEP is commonly and very effectively used to prevent the onset of

rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...

after a bite by a suspected-rabid animal, since diagnostic tools are not available to detect rabies infection prior to the onset of the nearly always-fatal disease. The treatment consists of a series of injections of

rabies vaccine The rabies vaccine is a vaccine used to prevent rabies. There are a number of rabies vaccines available that are both safe and effective. They can be used to prevent rabies before, and, for a period of time, after exposure to the rabies virus, ...

and

immunoglobulin An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

Rabies vaccine The rabies vaccine is a vaccine used to prevent rabies. There are a number of rabies vaccines available that are both safe and effective. They can be used to prevent rabies before, and, for a period of time, after exposure to the rabies virus, ...

is given to both humans and animals who have been potentially exposed to

Tetanus

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 usually ...

toxoid can be given in case of a suspected exposure to tetanus. In such cases, it can be given with or without tetanus

(also called ''tetanus antibodies'' or ''tetanus antitoxin''"tetanus"
in the ''

Encyclopædia Britannica The (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various time ...

''. Last Updated 7-17-2013). It can be given as

intravenous therapy Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutri ...

or by

intramuscular injection Intramuscular injection, often abbreviated IM, is the injection of a substance into a muscle. In medicine, it is one of several methods for parenteral administration of medications. Intramuscular injection may be preferred because muscles have ...

. The guidelines for such events in the United States for non-pregnant people 11 years and older are as follows:

HIV

History

AZT Zidovudine (ZDV), also known as azidothymidine (AZT), is an antiretroviral medication used to prevent and treat HIV/AIDS. It is generally recommended for use in combination with other antiretrovirals. It may be used to prevent mother-to-child ...

was approved as a treatment for

AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...

in 1987. Healthcare workers would occasionally be exposed to HIV during work. Some people thought to try giving health care workers AZT to prevent

seroconversion In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination. During infection or immunization, antigens enter the blood, and the adaptive immune system ...

. This practice dramatically decreased the incidence of seroconversion among health workers when done under certain conditions. Later the questions arose of whether to give HIV treatment after known exposure or high risk of exposure. Early data from pre-clinical studies established the efficacy of AZT in preventing transmission of HIV infection. AZT was also seen to reduce maternal-infant transmission of HIV in a

randomized controlled trial A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical te ...

, suggesting AZT's post-exposure prophylaxis (PEP) use. Subsequent data show combination antiretroviral therapy is significantly superior than AZT in reducing perinatal transmission rates. In addition, AZT is generally no longer recommended due to poor tolerance resulting in high rates of patient noncompliance. Non-occupational exposures include cases when a condom breaks while a person with HIV has sex with an HIV-negative person in a single incidence, or in the case of unprotected sex with an anonymous partner, or in the case of a non-habitual incident of sharing a syringe for

injection drug use Drug injection is a method of introducing a drug into the bloodstream via a hollow hypodermic needle, which is pierced through the skin into the body (usually intravenously, but also at an intramuscular or subcutaneous location). Intravenous t ...

. Evidence suggests that PEP also reduces the risk of HIV infection in these cases. In 2005, the US DHHS released the first recommendations for non-occupational PEP (nPEP) use to lower risk of HIV infection after exposures. The recommendations were replaced with an updated guideline in 2016. Occupational exposures include needlestick injury of health care professionals from an HIV-infected source. In 2012, the US DHHS included guidelines on occupational PEP (oPEP) use for individuals with HIV exposures occurring in health care settings. Since taking HIV-attacking medications shortly after exposure was proven to reduce the risk of contracting HIV, this led to research into

pre-exposure prophylaxis Pre-exposure prophylaxis (PrEP) is the use of medications to prevent the spread of disease in people who have not yet been exposed to a disease-causing agent, usually a virus. The term typically refers to the use of antiviral drugs as a strate ...

by taking medication before a potential exposure to HIV occurred. A report from early 2013 revealed that a female baby born with the HIV virus displayed no sign of the virus two years after high doses of three antiretroviral drugs were administered within 30 hours of her birth. The findings of the case were presented at the 2013 Conference on Retroviruses and Opportunistic Infections in

Atlanta Atlanta ( ) is the capital and most populous city of the U.S. state of Georgia. It is the seat of Fulton County, the most populous county in Georgia, but its territory falls in both Fulton and DeKalb counties. With a population of 498,715 ...

, U.S. and the baby is from

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...

, U.S. The baby—known as the "

Mississippi baby The Mississippi baby (born 2010) is a Mississippi girl who in 2013 was thought to have been cured of HIV. She had contracted HIV at birth from her HIV-positive mother. Thirty hours after the baby was born, she was treated with intense antiretr ...

"—was considered to be the first child to be "functionally cured" of HIV. However, HIV re-emerged in the child as of July 2014.

Risk evaluation

Initiation of post-exposure prophylaxis with the use of

antiretroviral The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs as a strategy to control HIV infection. There are several classes of antiretroviral agents that act on different stages of the HIV life-cycle. The use of multipl ...

drugs is dependent on a number of

risk factors In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...

, though treatment is usually started after one high-risk event. In order to determine whether post-exposure prophylaxis is indicated, an evaluation visit will be conducted to consider risk factors associated with developing

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...

. Assessments at this visit will include whether the at-risk person or the potential source-person are

HIV positive The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immu ...

, details around the potential HIV exposure event, including timing and circumstances, whether other high-risk events have occurred in the past, testing for

sexually transmitted diseases Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal diseases, are infections that are spread by sexual activity, especially vaginal intercourse, anal sex, and oral ...

, testing for

hepatitis B Hepatitis B is an infectious disease caused by the ''Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. Fo ...

and C (nPEP is also effective against

), and pregnancy tests for women of childbearing potential. Risk factors for developing HIV includes exposure of

mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

(vagina, rectum, eye, mouth, broken skin or under the skin) of an HIV-negative person to

bodily fluids Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the human body. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52-55%). ...

(blood, semen, rectal secretions, vaginal secretions, breast milk) of a person known to be

. For example, having

unprotected sex Safe sex is sexual activity using methods or contraceptive devices (such as condoms) to reduce the risk of transmitting or acquiring sexually transmitted infections (STIs), especially HIV. "Safe sex" is also sometimes referred to as safer sex ...

with

partner is considered risky, but sharing sex toys, spitting and biting considered to be negligible risks for initiating post-exposure prophylaxis. The highest non-sexual risk is

blood transfusion Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...

and the highest sexual contact risk is receptive anal intercourse. The timing of exposure does not affect the risk of developing HIV, but it does alter whether post-exposure prophylaxis will be recommended. Exposures that occurred 72 hours or less to beginning treatment are eligible for post-exposure prophylaxis. If the exposure occurred over 73 hours prior to treatment initiation, post-exposure prophylaxis is not indicated.

Testing

Initial HIV testing: Before initiating PEP after potential

exposure, persons should be tested for

HIV1 The subtypes of HIV include two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa, while HIV-2 viruses are related to viruses found in the sooty mangabey ...

and HIV2 antigens and antibodies in the blood using a

rapid diagnostic test A rapid diagnostic test (RDT) is a medical diagnostic test that is quick and easy to perform. RDTs are suitable for preliminary or emergency medical screening and for use in medical facilities with limited resources. They also allow point-of-care ...

. PEP should only be started if rapid diagnostic test reveals no HIV infection present or if tests results are not available. However, if HIV infection is already present then PEP should not be started. HIV test should be repeated four to six weeks and three months after exposure. People may experience signs and symptoms of

acute HIV infection The stages of HIV infection are acute infection (also known as primary infection), latency and AIDS. Acute infection lasts for several weeks and may include symptoms such as fever, swollen lymph nodes, inflammation of the throat, rash, muscle ...

, including fever, fatigue, myalgia, and skin rash, while taking PEP. CDC recommends seeking medical attention for evaluation if these signs and symptoms occur during or after the month of PEP. If follow-up laboratory antibody tests reveal HIV infection, HIV treatment specialists should be sought out and PEP should not be discontinued until person is evaluated and treatment plan is established. STI and HBV testing: People with potential exposure to HIV are also at risk of acquiring STI and HBV.

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...

(CDC) recommends STI-specific nucleic acid amplification testing ( NAAT) for

gonorrhea Gonorrhea, colloquially known as the clap, is a sexually transmitted infection (STI) caused by the bacterium '' Neisseria gonorrhoeae''. Infection may involve the genitals, mouth, or rectum. Infected men may experience pain or burning with ...

and

chlamydia Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium ''Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear they may occur only several wee ...

and blood tests for

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

. PEP is also active against HBV infections so discontinuation of medication can cause the reactivation of HBV, though rare. Health care providers must monitor HBV status closely. Follow up testing:

Serum creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an importa ...

and estimated

creatinine clearance Assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging. Functions of a healthy kidney include maintaining a person's fluid ...

should be measured at baseline to determine the most appropriate PEP antiretroviral regimen. While on PEP,

liver function Liver function tests (LFTs or LFs), also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient's liver. These tests include prothrombin time (PT/INR), activated partial thromboplastin tim ...

renal function Assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging. Functions of a healthy kidney include maintaining a person's fluid ...

, and hematologic parameters should be monitored.

Treatment

In the case of

exposure, post-exposure prophylaxis (PEP) is a course of

drugs which reduces the risk of

after events with high risk of exposure to HIV (e.g., unprotected

anal Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving s ...

vaginal sex Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...

needlestick injuries A needlestick injury is the penetration of the skin by a hypodermic needle or other sharp object that has been in contact with blood, tissue or other body fluids before the exposure. Even though the acute physiological effects of a needlestick i ...

, or sharing needles). The

CDC The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...

recommends PEP for any HIV-negative person who has recently been exposed to HIV for any reason. To be most effective, treatment should begin within an hour of exposure. After 72 hours PEP is much less effective, and may not be effective at all. Prophylactic treatment for HIV typically lasts four weeks. While there is compelling data to suggest that PEP after HIV exposure is effective, there have been cases where it has failed. Failure has often been attributed to the delay in receiving treatment (greater than 72 hours post-exposure), the level of exposure, and/or the duration of treatment (lack of adherence to the 28-day regimen). In addition, since the time and level of non-occupational exposures are self-reported, there is no absolute data on the administration timeframe to which PEP would be efficacious. The standard antibody window period begins after the last day of PEP treatment. People who received PEP are typically advised to get an antibody test at 6 months post-exposure as well as the standard 3 month test. The antiretroviral regimen used in PEP is the same as the standard

highly active antiretroviral therapy The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs as a strategy to control HIV infection. There are several classes of antiretroviral agents that act on different stages of the HIV life-cycle. The use of multip ...

used to treat AIDS. A typical prescription is a 28-day course of

emtricitabine/tenofovir Emtricitabine/tenofovir, sold under the brand name Truvada among others, is a fixed-dose combination antiretroviral medication used to treat and prevent HIV/AIDS. It contains the antiretroviral medications emtricitabine and tenofovir disopro ...

pills containing 200 mg of emtricitabine and 245 mg of tenofovir disoproxil to be taken once daily, and 400 mg pills of

raltegravir Raltegravir, sold under the brand name Isentress, is an antiretroviral medication used, together with other medication, to treat HIV/AIDS. It may also be used, as part of post exposure prophylaxis, to prevent HIV infection following potential ex ...

to be taken twice daily. People initiating nPEP treatment typically receive a 28-day starter pack, as opposed to a 3-7 day starter pack, to facilitate strong

medication adherence In medicine, patient compliance (also adherence, capacitance) describes the degree to which a patient correctly follows medical advice. Most commonly, it refers to medication or drug compliance, but it can also apply to other situations such as m ...

. They should also be counseled on the unpleasant side effects including malaise,

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...

headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

and

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...

. People at high risk for re-exposure due to unprotected intercourse or other behavioral factors should be given

PrEP PowerPC Reference Platform (PReP) was a standard system architecture for PowerPC-based computer systems (as well as a reference implementation) developed at the same time as the PowerPC processor architecture. Published by IBM in 1994, it allo ...

, which would begin immediately after the completion of the nPEP treatment course. Inversely, if a medically-adherent patient is already on PrEP upon non-occupational exposure, nPEP treatment is not necessary.

Hepatitis A

For exposure to

hepatitis A Hepatitis A is an infectious disease of the liver caused by ''Hepatovirus A'' (HAV); it is a type of viral hepatitis. Many cases have few or no symptoms, especially in the young. The time between infection and symptoms, in those who develop them ...

, human normal

(HNIG) and/or

hepatitis A vaccine Hepatitis A vaccine is a vaccine that prevents hepatitis A.Lay summary
...

may be used as PEP depending on the clinical situation.

Hepatitis B

If the person exposed is an

HBsAg HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates current hepatitis B infection. Structure and function The viral envelope of an enveloped virus has different sur ...

positive source (a known responder to HBV vaccine) then if exposed to

a booster dose should be given. If they are in the process of being vaccinated or are a non-responder they need to have

hepatitis B immune globulin Hepatitis B immunoglobulin (HBIG) is a human immune globulin, immunoglobulin that is used to prevent the development of hepatitis B and is used for the treatment of acute exposure to HBsAg. Medical uses HBIG is indicated as a postexposure prophyl ...

(HBIG) and the vaccine. For known non-responders HBIG and the vaccine should be given whilst those in the process of being vaccinated should have an accelerated course of HBV vaccine.

Hepatitis C

Persons exposed to

hepatitis C Hepatitis C is an infectious disease caused by the hepatitis C virus (HCV) that primarily affects the liver; it is a type of viral hepatitis. During the initial infection people often have mild or no symptoms. Occasionally a fever, dark urine, a ...

should be tested monthly with PCR, and if

occurs then treatment with

interferon Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten the ...

, or possibly

ribavirin Ribavirin, also known as tribavirin, is an antiviral medication used to treat RSV infection, hepatitis C and some viral hemorrhagic fevers. For hepatitis C, it is used in combination with other medications such as simeprevir, sofosbuvir, pegin ...

Anthrax

A 60-day course of oral

ciprofloxacin Ciprofloxacin is a fluoroquinolone antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain types of infectious diarrhea, respiratory tract infections, skin inf ...

should be given when exposure to

anthrax Anthrax is an infection caused by the bacterium ''Bacillus anthracis''. It can occur in four forms: skin, lungs, intestinal, and injection. Symptom onset occurs between one day and more than two months after the infection is contracted. The sk ...

is suspected.

Lyme disease

A single 200 milligram oral dose of

doxycycline Doxycycline is a broad-spectrum tetracycline class antibiotic used in the treatment of infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, Lyme disease, cholera, typhus, an ...

may be used within 3 days of a deer tick bite in a high risk area (such as

New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces ...

), if the tick was attached for at least 36 hours.

Monkeypox and Smallpox

The smallpox vaccine decreases the incidence of infection with

monkeypox Monkeypox (also called mpox by the WHO) is an infectious viral disease that can occur in humans and some other animals. Symptoms include fever, swollen lymph nodes, and a rash that forms blisters and then crusts over. The time from exposure t ...

and

smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) c ...

and the risk of severe illness even when administered after exposure. The CDC advises "that smallpox vaccine be given within 4 days from the date of exposure to prevent onset of the disease but should be offered up to 14 days post-exposure"; the NHS concurs with this but also urges to vaccinate as soon as possible after exposure.

References

External links

CDC on nonoccupational HIV postexposure prophylaxis
an article which summarizes more than 100 related research projects
HIV/AIDS Post-exposure prophylaxis
WHO
Occupational Postexposure Prophylaxis
: HRSA HIV/AIDS Bureau, The AIDS Education and Training Centers (AETC) {{DEFAULTSORT:Post-Exposure Prophylaxis Medical treatments HIV/AIDS Prevention of HIV/AIDS