Message from the Director: A few thoughts about PrEP and the TDF-2 Study
BOTUSA Director Dr. Margarett Davis
In this edition I want to highlight some important issues on PrEP, which stands for Pre-Exposure Prophylaxis. PrEP refers to an intervention that occurs before exposure to HIV that helps prevent HIV infection in an individual. It is an old concept; perhaps the best analogy is the use of pre-exposure prevention of malaria. Using this method, people take an anti-malarial pill on a daily or weekly basis to prevent malaria infection when they are in locations where malaria is a risk, such as northern Botswana and many other parts of Africa.
In PrEP, people take an ARV pill (antiretroviral drug or drugs) every day to prevent HIV infection. PrEP studies are being developed in Africa, the U.S., Thailand, and most recently in Peru and Ecuador, because this concept is very promising. I hasten to say that PrEP has been shown to be effective in preventing HIV ONLY in animal studies. The results were so striking that it is important to see whether this prevention approach could be effective for humans, too. Botswana has a very high prevalence of HIV infection so it is one of the best places to study this prevention method. It is also one of the places that can benefit most if PrEP is found to be effective.
BOTUSA is studying a form of PrEP in Gaborone and Francistown. This study is called TDF-2 and involves enrolling young sexually active people, aged 18-29 years, who are not infected with HIV and who, once screened and found eligible for the study, are randomly assigned to one of two groups. One of these groups takes an ARV drug called Truvada, and the other group takes a placebo (sugar pill). The study is double blinded so neither the researchers at BOTUSA nor the study subjects know which pill they are taking; the pills look alike. They receive intensive HIV prevention education and condoms, and are tested and followed carefully to watch for evidence of HIV infection. At the end of the study, the numbers of people in each group who have become HIV-infected are compared. If the number of HIV-infected people in the placebo group is statistically higher than the number of HIV-infected people in the Truvada group, the study will have shown that Truvada works to prevent HIV infection.
People have asked how the study subjects are exposed to HIV. Young men and women in the study are exposed to HIV in the community the same way they might be exposed if they were not in the study. To reduce their risk, the study subjects receive prevention education and condoms; it would be unethical not to provide the best prevention information we can to these young people. Because 25 percent of Batswana in the 15-49 year range are estimated to be HIV-positive, the risk of sexual contact with someone who is HIVpositive is very high. This is the reason why the study is so important.
Some have confused PrEP with a vaccine. PrEP is NOT a vaccine, but is an ARV pill taken for prevention. PrEP works directly on HIV by preventing it from growing inside the body. In contrast, a vaccine is given by injection or by mouth, but requires the human body to develop an immune response to fight the organism, in this case HIV. One of the reasons prevention measures like PrEP and circumcision are so important is that it is taking a very long time to develop an effective HIV vaccine. Estimates of 10-15 years for vaccine development have been given for the past 15 years. For PrEP we will have an answer in a few years, one way or the other.
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