Pre-exposure prophylaxis
Encyclopedia
Pre-exposure prophylaxis (PrEP) is any medical or public health procedure used before exposure to the disease causing agent, its purpose is to prevent, rather than treat or cure a disease. An example would be if a doctor gave a medication used to treat a disease to a healthy person who is not thought to have that disease, but is at risk for contracting it. More specifically, this practice is common with people who are about to travel from an area without malaria
to an area where malaria is a risk, and also it is being researched as a tool to prevent persons from contracting HIV
.
Pre-exposure prophylaxis can also refer to the aggressive use of vaccination
, for example in an attempt to prevent rabies
in people such as laboratory workers who are high risk for being bitten by rabid animals.
publishes recommendations for travels advising about the risk of contracting malaria in various countries.
Some of the factors in deciding whether to use chemotherapy as malaria PreP include the specific itinerary, length of trip, cost of drug, previous adverse reactions to antimalarials, drug allergies, and current medical history.
Studies of PrEP strategies in non-human primates have shown a reduced risk of infection among animals that receive ARVs prior to exposure to a simian form of HIV. A 2007 study at UT-Southwestern (Dallas) and the University of Minnesota
showed PrEP to be effective in "humanized" laboratory mice. Another rationale of PrEP comes from strategies to prevent mother-to-child transmission, which use ARVs given to the mother and the infant to help reduce the risk of transmission.
Today the two PrEP strategies under study are (1) a single drug called tenofovir disoproxil fumarate (TDF) and (2) a combination drug called Truvada , which combines TDF with the drug emtricitabine . Currently there are eight human trials of daily oral PrEP, with almost 20,000 participants currently or soon to be enrolled.
The CDC (Centers for Disease Control) is conducting an extended safety trial in the U.S., and expects the final data analysis to take place in early 2010 (see timeline).
There are several current and future PrEP challenges, from biomedical concerns (such as safety and effectiveness) to concerns of behavioral repercussions.
is the name of a specific clinical trial
completed in 2010 which demonstrated that PreP has some efficacy in reducing some people's risk of contracting HIV. It is notable for being the first PreP research project to announce this result.
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
to an area where malaria is a risk, and also it is being researched as a tool to prevent persons from contracting HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
.
Pre-exposure prophylaxis can also refer to the aggressive use of vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
, for example in an attempt to prevent rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...
in people such as laboratory workers who are high risk for being bitten by rabid animals.
PreP for malaria
The CDCCenters for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
publishes recommendations for travels advising about the risk of contracting malaria in various countries.
Some of the factors in deciding whether to use chemotherapy as malaria PreP include the specific itinerary, length of trip, cost of drug, previous adverse reactions to antimalarials, drug allergies, and current medical history.
PreP for HIV
Most commonly, the term "pre-exposure prophylaxis" refers to an experimental HIV-prevention strategy that would use antiretrovirals to protect HIV-negative people from HIV infection. PrEP is not proven to work; in the strategy that is currently being tested, HIV-negative people would take a single drug, or a combination of drugs, with the hopes that it would lower the risk of infection if exposed to HIV. Along with AIDS vaccines and microbicides, PrEP is one of the experimental HIV prevention strategies being tested in clinical trials today.Studies of PrEP strategies in non-human primates have shown a reduced risk of infection among animals that receive ARVs prior to exposure to a simian form of HIV. A 2007 study at UT-Southwestern (Dallas) and the University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...
showed PrEP to be effective in "humanized" laboratory mice. Another rationale of PrEP comes from strategies to prevent mother-to-child transmission, which use ARVs given to the mother and the infant to help reduce the risk of transmission.
Today the two PrEP strategies under study are (1) a single drug called tenofovir disoproxil fumarate (TDF) and (2) a combination drug called Truvada , which combines TDF with the drug emtricitabine . Currently there are eight human trials of daily oral PrEP, with almost 20,000 participants currently or soon to be enrolled.
The CDC (Centers for Disease Control) is conducting an extended safety trial in the U.S., and expects the final data analysis to take place in early 2010 (see timeline).
There are several current and future PrEP challenges, from biomedical concerns (such as safety and effectiveness) to concerns of behavioral repercussions.
Criticism of PreP
One criticism of PrEP for HIV is that it may encourage risky behavior including unprotected sex, possibly increasing, rather than decreasing, the risk of HIV infection in sero-discordant partners.iPrEx
iPrExIPrEx
The iPrEx study was a double-blind, placebo controlled Phase III clinical trial that began in 2007 following three years of community consultation. iPrEx was the first human efficacy study of pre-exposure prophylaxis to report efficacy data. iPrEx was sponsored by the U.S...
is the name of a specific clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
completed in 2010 which demonstrated that PreP has some efficacy in reducing some people's risk of contracting HIV. It is notable for being the first PreP research project to announce this result.
PreP as a Prevention
With an estimated 39.5 million people living with HIV worldwide and 4.3 million new infections per year, many people are at risk for HIV infection through sexual transmission, and therefore preemptive measures must be taken to prevent further dissemination. Pre-exposure prophylaxis (PrEP) supplies a promising prevention strategy for further sexual transmission. Although many trials in the past have failed to demonstrate the effectiveness of PrEP in HIV prevention, there are two promising treatments. One recent study indicated that the pill Truvada, made up of tenofovir and emtricitabine, reduced HIV transmission by 44% among sexually active men. Moreover, tenofovir in the form of a vaginal microbicide gel has been shown to slow HIV sexual transmission by 39%.External links
- PrEPWatch PrEP Watch homepage
- Singh JA, Mills EJ (2005) The Abandoned Trials of Pre-Exposure Prophylaxis for HIV: What Went Wrong? PLoS Med. 2(9): e234
- Lange J (2005) We Must Not Let Protestors Derail Trials of Pre-Exposure Prophylaxis for HIV PLoS Med. 2(9): e248.
- Aidsmap.com: Nevirapine studied as pre-exposure prophylaxis for HIV: safe in 200 mg dose
- Aidsmap.com: Pre-exposure prophylaxis may only offer limited benefit
- CDC: Rabies prevention and control