A Thailand trial has shown that a daily dose of the antiretroviral (ARV) drug Tenofovir reduces HIV incidence by almost half among injecting drug users and even further if they adhere to the regimen. The latest results complete the picture of Pre-Exposure Prophylaxis efficacy for all major HIV risk groups, showing that ARVs are protective.

Globally, there are around 16-million people inject drugs and three million of them are living with HIV. According to World Health Organisation statistics, on average, one out of every 10 new HIV infections is caused by injecting drug use and in parts of Eastern Europe and Central Asia over 80 per cent of all HIV infections is related to drug use.

The Thailand trial is the first to assess whether preventative treatment with HIV drugs could affect rates of HIV infection in people who inject drugs.

Published in The Lancet journal Online, the study results found that daily tablets of tenofovir reduced HIV incidence by 48.9 per cent compared to placebo. The protection was as high as 70 per cent in those who adhered to taking the drug as prescribed.

Over 2 400 participants were recruited at 17 drug treatment clinics in Bangkok, Thailand.  Around half of the participants (1204) were assigned a daily oral dose of tenofovir, and half (1209) were assigned placebo.  All trial participants were offered monthly HIV testing and risk-reduction counselling and services, plus access to drug rehabilitation treatment.

Participants were followed for an average of four years. Overall, 17 participants in the tenofovir group became infected with HIV, compared to 33 in the placebo group, indicating a reduction in HIV risk of 48.9%.  Further analyses of the results showed that the protective effect of the ARVs was best where participants adhered closely to the prescribing regime, reaching more than 70 per cent in this subgroup.

Previous studies have established that pre-exposure prophylaxis (PrEP) effectively reduces sexual transmission of HIV in both heterosexual couples and men who have sex with men, as well as reducing mother to child transmission of HIV.  However, this is the first study to show that this approach is also effective among people who inject drugs.

According to one of the researchers Dr Michael Martin, “This study completes the picture of PrEP efficacy for all major HIV risk groups – we now know that pre-exposure prophylaxis can be a potentially vital option for HIV prevention in people at very high risk for infection, whether through sexual transmission or injecting drug use.”

“Adherence was a key factor determining efficacy in our trial among people who inject drugs – as it has been in previous PrEP trials examining sexual transmission,” said Martin.  “These results underscore the importance of helping people using pre-exposure prophylaxis achieve effective levels of adherence.”

Writing in a linked Comment in The Lancet, Professor Salim Karim, Director of the Centre for the AIDS Programme of Research in South Africa (CAPRISA) at the University of KwaZulu-Natal, says that the reduction in HIV infections reported here may not be specifically attributable to a protective effect of the antivirals on people who become infected through injecting drugs.  Some injecting drug users engage in risky sexual behaviour, such as selling sex to fund their drug habit, so it is possible that the protective effect observed in this trial is at least partly attributable to the already established positive effects of PrEP on sexual transmission of HIV.

However, according to Karim, “Even though questions remain about the extent to which PrEP can be effective in preventing either of the routes of transmission in this group, the overall result is that daily tenofovir does reduce HIV transmission in injecting drug users. The introduction of PrEP for HIV prevention in injecting drug users should be considered as an additional component to accompany other proven prevention strategies like needle exchange programmes, methadone programmes, promotion of safer sex and injecting practices, condoms, and HIV counselling and testing.”

AVAC will be hosting a webinar to help explain the results and next steps on Tuesday the 18th at 10am EDT (visit www.timeanddate.com to confirm the time in your area). 

Register here https://cc.readytalk.com/cc/s/registrations/new?cid=7le50dlg7kjj

PRESS STATEMENT:  UNAIDS welcomes new findings that provide an additional tool for HIV prevention for people who inject drugs

UNAIDS PrEP press release (pdf)