Almost three-quarters of AIDS cases worldwide are in Africa, especially sub-Saharan Africa. Women represent about half of all HIV infections globally; young women are particularly at risk.
So far, trials of microbicides -- compounds to be applied to the vagina or rectum to prevent infection with sexually transmitted diseases (STDs) -- have been disappointing.
Eleven trials in the past 15 years have shown no change or even sometimes an increase in transmission rates, said study co-author Quarraisha Abdool Karim, associate director of CAPRISA and an associate professor of epidemiology at the Columbia University Mailman School of Public Health in New York City.
Quarraisha Abdool Karim and Salim S. Abdool Karim are married.
For this study, close to 900 HIV-negative women aged 18 to 40 in urban and rural KwaZulu-Natal, South Africa, an epicenter of the AIDS epidemic, were randomized to take the Viread gel or a placebo gel.
Participants were told to administer two doses of the gel: one within 12 hours before sex and one within 12 hours after sex.
The trial lasted almost three years.
Overall, the gel reduced HIV infection by 39 percent. But in women who had high adherence (using the gel more than 80 percent of the time), the risk reduction was 54 percent, compared to women in the placebo group.
"Without this gel, for every 100 women we may see 10 women being infected in a year," said Salim S. Abdool Karim. "With this gel, we would see only six women being infected."
The gel also reduced the risk of contracting genital herpes by 51 percent, a factor which could slow the spread of HIV even further, given that people with genital herpes have double the risk of getting HIV, said Salim S. Abdool Karim.
The gel appeared to be less effective after 18 months. "We think the dim
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