Results from trial on pre-exposure prophylaxis among people who inject drugs

WHO welcomes positive results from the Bangkok trial that investigated effects of oral pre-exposure prophylaxis (PrEP) for HIV prevention among people who inject drugs (PWID). The U.S. Centers for Disease Control, the Bangkok Metropolitan Administration and the Thai Ministry of Public Health have reported today that daily oral PrEP among PWID reduces the risk of acquiring HIV by approximately 49%. The reduction was 74% among those with higher adherence.

Based on findings from previous studies, WHO’s current guidance on oral PrEP recommends it for serodiscordant couples, men and transgender women who have sex with men and who are at high risk of HIV, for use in the context of demonstration projects. Following results from this study, WHO will explore how best PrEP could be applied among injecting drug users in combination with other, specifically harm reduction, interventions. WHO will continue to work with countries to learn how these exciting findings can best be used in combination with other prevention interventions to protect the lives of those most at risk of HIV.

About the Bangkok trial

The double blinded trial was begun in 2005 and recruited more than 2 400 HIV uninfected men and women who reported injecting drugs in the previous year to participate in the trial. These people were randomized to one of two arms: 1,204 were assigned to receive one 300 mg tablet of tenofovir disoproxil fumarate daily and 1,209 were assigned to take one placebo tablet daily.

All participants were offered extensive HIV education and risk-reduction counseling, methadone, HIV counseling and testing, condoms and bleach with instructions on how to clean needles at monthly study visits. Sterile syringes, one of the most effective means of HIV prevention for PWID, were not provided, in keeping with Thai government policy. Sterile syringes are however available at pharmacies, at low cost and without prescription.

Participants’ health was monitored and referrals for needed care were made. Any participants who seroconverted during the trial were referred for HIV care and treatment through the Thai national health system. Adherence overall in the study was high. Participants had the option of directly observed pill taking (DOT) and used this 87% of the time. Study diaries were also kept, combining both the DOT and non-DOT time. These indicate that participants took the drug on 84% of days in the study. No adherence difference was found between the tenofovir and placebo arms.

Participants were followed for an average of 5 years, with some in the trial for almost 7 years. No significant safety concerns associated with daily oral PrEP use were reported. No significant differences were reported in risk behavior between the two arms. Both injection and sexual risk declined substantially during the trial. Reported drug injecting in the previous 12 weeks decreased from 63%at baseline to 23% at one year. Needle sharing decreased from 18% to 2%. Proportion reporting sex with more than one partner in the past 12 weeks decreased from 22% to 11%.