A follow-up to the international study that prompted support for PrEP to prevent HIV has found only a third of those participating took a dose of Truvada every day, the key requirement of pre-exposure prophylaxis. Three months after the beginning of the study only about 40 percent of participants were taking a sufficient quantity of the medicine to protect them from HIV infection.
That data was presented today at the 20th International AIDS Conference (AIDS 2014) in Melbourne, Australia.
Researchers in the follow-up study found no HIV infection in participants who took Truvada four or more times a week. Those who took the pill two to three times a week reduced their risk of contracting HIV by 84 percent. Those who took fewer than two pills a week showed no reduction in risk of contracting HIV.
The likelihood that one would take the medicine as prescribed correlated closely with age. Those in their 30s and 40s were two or three times more likely to take Truvada daily than were those who were younger.
Earlier this month the World Health Organization endorsed PrEP as a strategy for reducing the rate of infection with HIV. In May the federal Centers for Disease Control also endorsed PrEP as a way to reduce HIV infection.
The study released at the International AIDS Conference would seem to buttress concerns raised by Michael Weinstein, president of the AIDS Healthcare Foundation, the world’s largest non-government supplier of HIV services. Weinstein has said he fears the promotion of PrEP as an HIV prevention tool by Gilead, the pharmaceutical company that manufactures it, and various government agencies and HIV/AIDS organizations will lead to gay men not using condoms. When used properly, condoms have been proven to be the most effective barrier to transmission of HIV, given that the virus cannot penetrate latex. Weinstein has questioned whether gay men will adhere to the requirement that they take a pill every day to protect themselves from HIV infection during unpredictable future sexual encounters.
Weinstein and others also have said that too great a reliance on Truvada and less of a focus on condoms will lead to an increase in sexually transmitted diseases such as syphilis and gonorrhea, a drug-resistant strain of which has been detected in San Francisco.