Johannesburg - A trial in Thailand has shown that a daily dose of the antiretroviral (ARV) drug tenofovir reduces HIV incidence by nearly 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 (PrEP) for all major HIV-risk groups, showing ARVs are protective.
Globally, about 16 million people inject drugs, and 3 million of them are living with HIV. World Health Organisation statistics show that 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 percent of all HIV infections is related to drug use.
The Thai trial is the first to assess whether preventive treatment with HIV drugs could affect rates of HIV infection in people injecting drugs.
Published in The Lancet journal online, the study results found that daily tablets of tenofovir reduced HIV incidence by 48.9 percent compared to a placebo. The protection was as high as 70 percent in those who adhered to taking the drug as prescribed.
Over 2 400 participants were recruited at 17 drug treatment clinics in Bangkok, Thailand. About half the participants (1 204) were assigned a daily oral dose of tenofovir, and half (1 209) were assigned a 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 about 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 percent.
Further analysis of the results showed that the protective effect of the ARVs was best when participants adhered strictly to the prescribing regime, reaching more than 70 percent in this subgroup.
In a linked comment in The Lancet, Professor Salim Karim, director of the Centre for the Aids Programme of Research in South Africa at the University of KwaZulu-Natal, says the reduction in HIV infections reported may not be specifically attributable to a protective effect of the ARVs on people infected by injecting drugs.
He said some injecting drug-users engage in risky sexual behaviour, such as selling sex to fund their drug habit, so it is possible the protective effect is at least partly attributable to the established positive effects of PrEP on sexual transmission of HIV. - Health-e News Service