New PReP Efficacy Study Released

A new study on the efficacy of Truvada as an daily HIV preventive was released yesterday at the International AIDS Conference in Melbourne, Australia. According the research, which was simultaneously published in The Lancet, missing an occasional daily dose does not increase the chance of infection, but the drug must be taken at least four times a week in order maintain a blood level that blocks HIV.

While the effectiveness of PrEP was first proven in 2010, there had been some concern that it might not be safe to use long term. There was also speculation that access to PrEP could either cause individuals to increase risky sexual behaviour or be reluctant to use it. But the latest study found no evidence of “risk compensation”. It also found that there was an interest and willingness to use the preventative method by those at high risk of HIV-infection.

Tested on more than 1 600 HIV-negative men, including gay men, bisexuals, transgender women and men-sleeping-with men (MSM) at 11 research sites on four different continents, the latest study found that PrEP provided 100 percent protection among participants who took the pill four times or more every week. Those who took the pill two or three times a week registered a protection rate of about 84 percent. Those who took fewer than two tablets in the same period had no protection at all.

Carried out by the US-based National Institute of Health over an 18-month period in Chicago, San Fransisco, Boston, Thailand, Rio de Janeiro and Cape Town, among other sites, researchers are convinced that using pre-exposure prophylaxis could save lives of high-risk populations. ay men are regarded as the key population or at highest risk of HIV infection and transmission. At the conference it also emerged that while the HIV/Aids burden was declining in parts of the world, HIV infection among gay men was increasing.

Here’s another take from AIDS Map:

The group of gay men and transgender women in this study who elected to take a daily Truvada pill had half as many HIV infections (relative risk = 0.51) compared with a comparator group of people who elected to stay in the study but not to take PrEP. They also had half the HIV infection rate (relative risk = 0.49) of people in the placebo arm of the original iPrEx randomised controlled trial (RCT). As has been seen in other studies of pre-exposure prophylaxis (PrEP), as well as in the original iPrEx RCT, the primary determining factor when it came to the efficacy of PrEP was adherence.

All participants in iPrEx OLE had their level of adherence calculated from drug levels observed in blood samples. PrEP had so significant efficacy in people who took fewer than two doses a week. However, the efficacy of PrEP was 84% in people who took 2-3 doses a week – there was only one infection in this group – and no infections at all were seen in people taking at least four doses a week. This 100% efficacy translates into a minimum efficacy of 86% if the statistical uncertainty of the result is taken into account.