Post-exposure prophylaxis

Post-exposure prophylaxis or post-exposure prevention (PEP) is any preventive medical treatment started immediately after exposure to a pathogen (such as a disease-causing virus), in order to prevent infection by the pathogen and the development of disease.

Rabies
PEP is commonly and very effectively used to prevent the outbreak of rabies after a bite by a rabid animal. The treatment consists of repeated injections of rabies vaccine and immunoglobulin. Rabies vaccine is given to both humans and animals who have been potentially exposed to rabies.

Tetanus
Tetanus post-exposure consists of 2 to 3 injections of tetanus vaccine and tetanus immunoglobulin.

History
AZT was approved as a treatment for AIDS in 1987. As AIDS patients started seeking treatment in medical centers, it sometimes happened that a healthcare worker would be exposed to HIV during work. Some people thought to try giving health care workers AZT to prevent seroconversion. This practice dramatically decreased the incidence of seroconversion among health workers when done under certain conditions.

Later the question arose of whether to give HIV treatment to people who had non-occupational exposure, for example, when a condom breaks while a person with HIV has unprotected 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.

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, which would mean taking medication before any exposure to HIV in anticipation of being in a situation which was likely to expose one to HIV infection.

Risk evaluation
Risk factor must be considered in order to consider the individual as a candidate for HIV post-exposure prophylaxis. For example, having unprotected sex with HIV positive partner is considered risky, but sharing sex toys, spitting and biting considered to be negligible risk for evaluation of pep. The highest non-sexual risk is involve blood transfusion and the highest among sexual contact involve receptive anal intercourse.

Treatment
In the case of HIV exposure, post-exposure prophylaxis is a course of antiretroviral drugs which reduces the risk of seroconversion after events with high risk of exposure to HIV (e.g., unprotected anal or vaginal sex, needlestick injuries, or sharing needles). The CDC 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 post-exposure 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, duration of treatment (lack of adherence to the 28 day regimen), or all three. However, given that&mdash;for non-occupational exposures&mdash;the time and level of exposure are based on patient-supplied information, absolute data is unavailable. The standard antibody window period begins after the last day of PEP treatment. Doctors will advise patients who received PEP 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 used to treat AIDS. It requires close compliance and can have unpleasant side effects including malaise, fatigue, diarrhea, headache, nausea and vomiting.

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, U.S. and the baby is from Mississippi, 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.

Hepatitis A
For exposure to hepatitis A, human normal immunoglobulin (HNIG) and/or hepatitis A vaccine may be used as PEP depending on the clinical situation.

Hepatitis B
If the person exposed is an HBsAg positive source (a known responder to HBV vaccine) then if exposed to hepatitis B 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 should get monthly PCR, and if seroconversion occurs then interferon, with possible ribavirin.