| Post-exposure prophylaxis | |
|---|---|
| Other names | Post-exposure prevention |
Post-exposure prophylaxis, also known aspost-exposure prevention (PEP), is anypreventive medical treatment started after exposure to apathogen in order to prevent the infection from occurring.
It should be contrasted withpre-exposure prophylaxis, which is used before the patient has been exposed to the infective agent.
In 2021, the USFDA gaveemergency use authorization (EUA) tobamlanivimab/etesevimab for post-exposure prophylaxis againstCOVID-19.[1] However, due to its reduced effectiveness againstOmicron variants of the SARS-CoV-2 virus, it is no longer recommended for this purpose.[2]
Ensitrelvir has been studied for its potential use as post-exposure prophylaxis against COVID-19 in a phase 3 clinical trial.[3][4][5] 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.[6][7][8]
PEP is commonly and very effectively used to prevent the onset ofrabies 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.[9] The treatment consists of a series of injections ofrabies vaccine andimmunoglobulin.[10]Rabies vaccine is given to both humans and animals who have been potentially exposed torabies.[11]
As of 2018, the average estimated cost of rabies post-exposure prophylaxis was US$108 (along with travel costs and loss of income).[12]
Tetanus toxoid can be given in case of a suspected exposure to tetanus. In such cases, it can be given with or without tetanusimmunoglobulin (also calledtetanus antibodies ortetanus antitoxin[13]). It can be given asintravenous therapy or byintramuscular injection.[citation needed]
The guidelines for such events in the United States for non-pregnant people 11 years and older are as follows:[14]
| Vaccination status | Clean, minor wounds | All other wounds |
|---|---|---|
| Unknown or fewer than three doses of tetanus toxoid containing vaccine | Tdap and recommend catch-up vaccination | Tdap and recommend catch-up vaccination Tetanusimmunoglobulin |
| Three or more doses of tetanus toxoid containing vaccine AND less than 5 years since last dose | No indication | No indication |
| Three or more doses of tetanus toxoid containing vaccine AND 5–10 years since last dose | No indication | Tdap preferred (if not yet received) or Td |
| Three or more doses of tetanus toxoid containing vaccine AND more than 10 years since last dose | Tdap preferred (if not yet received) or Td | Tdap preferred (if not yet received) or Td |
AZT was approved as a treatment forAIDS in 1987. Healthcare workers would occasionally be exposed toHIV during work. Some people[who?] thought to try giving health care workers AZT to preventseroconversion. This practice dramatically decreased the incidence of seroconversion among health workers when done under certain conditions.[15]
Later the questions arose of whether to give HIV treatment after known exposure or high risk of exposure. Early data frompreclinical studies established the efficacy of AZT in preventing transmission of HIV infection.[16] AZT was also seen to reduce maternal-infant transmission of HIV in arandomized controlled trial, suggesting AZT's post-exposure prophylaxis (PEP) use.[17] Subsequent data showcombination antiretroviral therapy is significantly superior than AZT in reducing perinatal transmission rates.[18] In addition, AZT is generally no longer recommended due to poor tolerance resulting in high rates of patient noncompliance.[citation needed]
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 forinjection drug use. Evidence suggests that PEP also reduces the risk of HIV infection in these cases.[19] In 2005, theUS 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.[20]
Occupational exposures include needlestick injury of health care professionals from an HIV-infected source. In 2012, theUS DHHS included guidelines on occupational PEP (oPEP) use for individuals with HIV exposures occurring in health care settings.[21]
Since taking HIV-attacking medications shortly after exposure was proven to reduce the risk of contracting HIV, this led to research intopre-exposure prophylaxis by taking medication before a potential exposure to HIV occurred.[22]
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 inAtlanta, U.S. and the baby is fromMississippi, U.S. The baby—known as the "Mississippi baby"—was considered to be the first child to be "functionally cured" of HIV.[23] However, HIV re-emerged in the child as of July 2014.[24]
Initiation of post-exposure prophylaxis with the use ofantiretroviral drugs is dependent on a number ofrisk factors, 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 developingHIV. Assessments at this visit will include whether the at-risk person or the potential source-person areHIV positive, details around the potential HIV exposure event, including timing and circumstances, whether other high-risk events have occurred in the past, testing forsexually transmitted diseases, testing forhepatitis B andC (nPEP is also effective againsthepatitis B), and pregnancy tests for women of childbearing potential.[20]
Risk factors for developing HIV includes exposure ofmucous membranes (vagina, rectum, eye, mouth, broken skin or under the skin) of an HIV-negative person tobodily fluids (blood, semen, rectal secretions, vaginal secretions, breast milk) of a person known to beHIV positive. For example, havingunprotected sex withHIV positive 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 isblood transfusion 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.[20]
Initial HIV testing: Before initiating PEP after potentialHIV exposure, persons should be tested forHIV1 andHIV2 antigens and antibodies in the blood using arapid diagnostic test. 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.[20]
People may experience signs and symptoms ofacute 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.[20]
STI and HBV testing: People with potential exposure to HIV are also at risk of acquiringSTI andHBV.Centers for Disease Control and Prevention (CDC) recommends STI-specific nucleic acid amplification testing (NAAT) forgonorrhea andchlamydia and blood tests forsyphilis. PEP is also active against HBV infections so discontinuation of medication can cause the reactivation ofHBV, though rare. Health care providers must monitor HBV status closely.[20]
Follow up testing:Serum creatinine and estimatedcreatinine clearance should be measured at baseline to determine the most appropriate PEP antiretroviral regimen. While on PEP,liver function,renal function, and hematologic parameters should be monitored.[20]
In the case ofHIV exposure, post-exposure prophylaxis (PEP) is a course ofantiretroviral drugs which reduces the risk ofseroconversion after events with high risk of exposure to HIV (e.g., unprotectedanal orvaginal sex,needlestick injuries, orsharing needles).[25] TheCDC recommends PEP for any HIV-negative person who has recently been exposed to HIV for any reason.[25]
To be most effective, treatment should begin within an hour of exposure.[26] After 72 hours PEP is much less effective, and may not be effective at all.[25] Prophylactic treatment for HIV typically lasts four weeks.[25][27]
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.[25]
The antiretroviral regimens used in PEP are the same as commonhighly active antiretroviral therapies used to treat HIV/AIDS. As of May 2025, CDC Guidelines recommend that adults and adolescents without contraindications receive a 28-day, once-daily regimen consisting of either:[28][29]
People initiating nPEP treatment typically receive a 28-day starter pack rather than a 3–7 day starter pack, to facilitate strongmedication adherence.[20] They should also be counseled on unpleasant side effects includingmalaise,fatigue,diarrhea,headache,nausea,vomiting, andinsomnia, depending on the medication administered.[25][30]
People at high risk for re-exposure due to unprotected intercourse or other behavioral factors should beginPrEP 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.[20]
For exposure tohepatitis A, human normalimmunoglobulin (HNIG) and/orhepatitis A vaccine may be used as PEP depending on the clinical situation.[31][32]
If the person exposed is anHBsAg positive source (a known responder toHBV vaccine) then if exposed tohepatitis B a booster dose should be given. If they are in the process of being vaccinated or are a non-responder they need to havehepatitis 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.[citation needed][33]
 | This section needs to beupdated. The reason given is: new generation antiviral drugs for Hepatitis C negate the need for Interferon and Ribavirin. Please help update this article to reflect recent events or newly available information.(April 2023) |
Persons exposed tohepatitis C should be tested monthly withPCR, and ifseroconversion occurs then treatment withinterferon, or possiblyribavirin.[citation needed]
A 60-day course of oralciprofloxacin should be given when exposure toanthrax is suspected.[34]
A single 200 milligram oral dose ofdoxycycline may be used within 3 days of adeer tick bite in a high risk area (such asNew England), if the tick was attached for at least 36 hours.[35][36][37]
The smallpox vaccine decreases the incidence risk of severe illness when administered after exposure tompox andsmallpox. 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.[38]
SCORPIO-PEP is a 28-day study to assess the prevention of COVID-19 infection in those who have been exposed through household contact.
We recommend that prophylactic antibiotic therapy be given only to adults and children within 72 hours of removal of an identified high-risk tick bite, but not for bites that are equivocal risk or low risk (strong recommendation, high-quality evidence). comment: If a tick bite cannot be classified with a high level of certainty as a high-risk bite, a wait-and-watch approach is recommended. A tick bite is considered to be high-risk only if it meets the following three criteria: the tick bite was from (a) an identified Ixodes spp. vector species, (b) it occurred in a highly endemic area, and (c) the tick was attached for ≥36 hour
Vaccination should be administered as soon as possible and within 4 days after an identified exposure to prevent or attenuate infection.