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 (, "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 theory of d ...

in order to prevent the infection from occurring. It should be contrasted with

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. Vaccination is the most commonly used form of pre-exposure prophylaxis; other forms of ...

, which is used before the patient has been exposed to the infective agent.

COVID-19

In 2021, the US

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 ...

gave emergency use authorization (EUA) to bamlanivimab/etesevimab for post-exposure prophylaxis against

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 can vary but often include fever ...

. However, due to its reduced effectiveness against Omicron variants of the SARS-CoV-2 virus, it is no longer recommended for this purpose. Ensitrelvir has been studied for its potential use as post-exposure prophylaxis against COVID-19 in a phase 3 clinical trial. Top-line results from this trial suggested that use of ensitrelvir as post-exposure prophylaxis may significantly reduce the risk of symptomatic COVID-19 infection in exposed household contacts compared to placebo.

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. It was historically referred to as hydrophobia ("fear of water") because its victims panic when offered liquids to drink. Early symptoms can include fever and abn ...

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 several rabies vaccines available that are both safe and effective. Vaccinations must be administered prior to rabies virus exposure or within the Latent period (epidemiology), l ...

and

immunoglobulin An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

Rabies vaccine The rabies vaccine is a vaccine used to prevent rabies. There are several rabies vaccines available that are both safe and effective. Vaccinations must be administered prior to rabies virus exposure or within the Latent period (epidemiology), l ...

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

. As of 2018, the average estimated cost of rabies post-exposure prophylaxis was US$ 108 (along with travel costs and loss of income).

Tetanus

Tetanus Tetanus (), also known as lockjaw, is a bacterial infection caused by ''Clostridium tetani'' and 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 l ...

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''). 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 nutr ...

or by

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

. 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), was the first 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 vertica ...

was approved as a treatment for

AIDS The HIV, human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system. Without treatment, it can lead to a spectrum of conditions including acquired immunodeficiency syndrome (AIDS). It is a Preventive healthcare, pr ...

in 1987. Healthcare workers would occasionally be exposed to

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 im ...

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 immune system begins t ...

. 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 preclinical 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 ...

, 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. 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

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 List of capitals in the United States, capital and List of municipalities in Georgia (U.S. state), most populous city in the U.S. state of Georgia (U.S. state), Georgia. It is the county seat, seat of Fulton County, Georg ...

, U.S. and the baby is from

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

, U.S. The baby—known as the " Mississippi baby"—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 mu ...

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 ...

, 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

. 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 AIDS, acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of th ...

, 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 A sexually transmitted infection (STI), also referred to as a sexually transmitted disease (STD) and the older term venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, 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. ...

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 body of an organism. 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 ...

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

. For example, having unprotected 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 Circulatory system, circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used ...

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 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 Screening (medicine), medical screening and for use in medical facilities with limited resources. They als ...

. 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 testing should be repeated four to six weeks and three months after exposure. People may experience signs and symptoms of acute HIV infection, 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 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) recommends STI-specific nucleic acid amplification testing (

NAAT A nucleic acid test (NAT) is a technique used to detect a particular nucleic acid sequence and thus usually to detect and identify a particular species or subspecies of organism, often a virus or bacterium that acts as a pathogen in blood, Tissue ...

) for

gonorrhea Gonorrhoea or 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. Gonorrhea is spread through sexual c ...

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 w ...

and blood tests for

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms depend on the stage it presents: primary, secondary, latent syphilis, latent or tertiary. The prim ...

. 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 impor ...

and estimated creatinine clearance should be measured at baseline to determine the most appropriate PEP antiretroviral regimen. While on PEP, liver function,

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 flu ...

, 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 or

vaginal sex In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The vaginal int ...

, needlestick injuries, 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 (HHS), and is headquartered in Atlanta, ...

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 mul ...

used to treat AIDS. A typical prescription is a 28-day course of emtricitabine/tenofovir pills containing 200 mg of emtricitabine and 245 mg of tenofovir disoproxil to be taken once daily, along with either 50 mg of dolutegravir once daily or 400 mg 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 e ...

twice daily. People initiating nPEP treatment typically receive a 28-day starter pack rather than a 3–7 day starter pack, to facilitate strong medication adherence. They should also be counseled on unpleasant side effects including

malaise In medicine, malaise is a feeling of general discomfort, uneasiness or lack of wellbeing and often the first sign of an infection or other disease. It is considered a vague termdescribing the state of simply not feeling well. The word has exist ...

fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

headache A headache, also known as cephalalgia, 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 (mood), depression in those with severe ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

vomiting Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...

, and

insomnia Insomnia, also known as sleeplessness, is a sleep disorder where people have difficulty sleeping. They may have difficulty falling asleep, or staying asleep for as long as desired. Insomnia is typically followed by daytime sleepiness, low ene ...

, depending on the medication administered. People at high risk for re-exposure due to unprotected intercourse or other behavioral factors should begin

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 allow ...

immediately after the completion of the nPEP treatment course. Conversely, if a medically adherent patient is already taking PrEP medication upon non-occupational exposure, nPEP treatment is not necessary.

Hepatitis A

For exposure to

hepatitis A Hepatitis A is an infectious liver disease caused by Hepatitis A virus (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, is ...

, human normal

(HNIG) and/or

hepatitis A vaccine Hepatitis A vaccine is a vaccine that prevents hepatitis A. It is effective in around 95% of cases and lasts for at least twenty years and possibly a person's entire life. If given, two doses are recommended beginning after the age of one. It ...

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 existing hepatitis B infection. Structure and function The viral envelope of an enveloped virus has different su ...

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 (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 period, people often have mild or no symptoms. Early symptoms can include ...

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 ...

, or possibly

ribavirin Ribavirin, also known as tribavirin, is an antiviral medication used to treat illness caused by respiratory syncytial virus (RSV) and hepatitis C virus (HCV) infections, as well as some viral hemorrhagic fevers. For HCV, it is used in combi ...

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 ...

should be given when exposure to

anthrax Anthrax is an infection caused by the bacterium '' Bacillus anthracis'' or ''Bacillus cereus'' biovar ''anthracis''. Infection typically occurs by contact with the skin, inhalation, or intestinal absorption. Symptom onset occurs between one ...

is suspected.

Lyme disease

A single 200 milligram oral dose of

doxycycline Doxycycline is a Broad-spectrum antibiotic, broad-spectrum antibiotic of the Tetracycline antibiotics, tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat pneumonia, bacterial p ...

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 consisting of 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 (state), New York to the west and by the ...

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

Poxviruses

The smallpox vaccine decreases the incidence risk of severe illness when administered after exposure to

mpox Mpox (, ; formerly known as monkeypox) is an infectious viral disease that can occur in humans and other animals. Symptoms include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. The illness is usually mild, ...

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 (W ...

. 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 Prevention of HIV/AIDS