In 2007, a study to test the safety and efficacy of pre-exposure prophylactic (PrEP) treatment for the prevention of HIV, called TDF2, began in Botswana. While the study was expected to last four to six years, the Centers for Disease Control and Prevention (CDC) announced in December 2009, that the study had to be changed due to unforeseen circumstances.
About the TDF2 Study in Botswana
The TDF2 study is run by BOTUSA, a collaboration between the Botswana Ministry of Health and CDC in the US. The study was designed to review the safety and efficacy of using tenofovir and emtricitabine as PrEP. As a randomized, double-blind, placebo controlled trial, all participants received risk reduction counseling and other prevention services, but half the group was also assigned to receive medication.
TDF2 intended to enroll 2,200 HIV-negative heterosexual men and women between the ages of 18 to 39 from Botswana’s two largest cities, Gaborone and Francistown. Participants were recruited from HIV testing and counseling center, family planning clinics, youth organizations, and community events. The study is run by BOTUSA, a collaboration between the Botswana Ministry of Health and the CDC in the United States.
Problems with the TDF2 Study
Two major factors have contributed to the problems that the TDF2 is experiencing. First, the overall HIV rate in Botswana has been steadily declining. This is due to rang of HIV preventative services available, especially in large cities. The original sample size needed to determine if there is a difference in the HIV rate for those receiving medication and those receiving just services is no longer enough to detect the necessary difference between the two methods.
The second challenge has been participant retention. Reasons for leaving the study include pregnancy, relocation, and high time demands. While BOTUSA has worked hard to listen to participants and overcome challenges, many participants have chosen to leave the study despite efforts to make clinic hours more accessible and increasing payment to participants.
While recruiting more participants to study was considered, researchers found that they would have to more than double the number of participants in order to test the efficacy of the treatment. Finding this many more volunteers would be difficult and costly. In addition, due to the low retention rate, it is not clear that they would be able to retain enough of them to make a difference.
New Plans for the TDF2 Study
Despite setbacks, the TDF2 study plans to continue. While efficacy of the PrEP treatment can no longer be established, the trial will still provide useful information. Researchers are still planning to look at the safety of the treatment, as well as behavioral factors related to adherence. Since patients will not need to be followed as long to examine these goals, demands on volunteers may diminish.
The TDF2 study has two other arms, one in Thailand and one in the US, that are on track to be completed as originally planned. These two studies will provide insight on the use of PrEP using different medications in various populations.
References:
CDC. Status of the Botswana TDF2 Study of Pre-Exposure Prophylaxis for HIV Prevention. December 2009.
CDC. CDC Trials of Pre-Exposure Prophylaxis for HIV Prevention. August 21, 2009.
Jamie Robertson - Jamie Robertson has worked and volunteered for HIV/AIDS organization for over 5 years. Her work has taken her throughout the United States ...
