May 12, 2011 -- People who start HIV treatment while their immune systems still are strong are 27 times less likely to infect their sex partner than are those who delay treatment, an international study shows.
Nearly all of the people who volunteered for the study -- 97% -- were heterosexual couples. This makes it impossible to say whether the findings also apply to same-sex couples.
Even so, the study has major implications for preventing the sexual spread of HIV. Most of the world's 2.6 million new HIV infections each year occur via heterosexual sex. It's long been suspected that treatment makes a person less infectious; this is the first clinical trial to prove it.
"These findings strongly indicate that treating an individual sooner rather than later can reduce the risk of HIV transmission to a sex partner," Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), said at a news conference. The NIAID funded the $73 million study.
Currently, the decision on how soon a person should begin HIV treatment is based on how much treatment will benefit the patient. Guidelines suggest starting treatment when a person's CD4 T-cell count -- a measure of immune competence -- is 350 to 500 cells per cubic millimeter of blood. Immediate treatment is advised for anyone whose T-cell count drops below 350.
The study enrolled 1,763 couples in 13 sites in Botswana, Brazil, India, Kenya, Malawi, South Africa, Thailand, the U.S., and Zimbabwe. Each couple had one partner who was uninfected and another who was infected with HIV and had a CD4 count of 350 to 500.
Half of the infected partners immediately began therapy with a combination of three HIV drugs (the exact combination varied from nation to nation and included 11 different drugs). The other HIV-infected partners delayed treatment until their CD4 count dropped to 250 or until they showed signs of an AIDS-related infection. All couples were provided free condoms and given safe-sex information.
The study began in 2005 and was supposed to continue to 2015. But an interim analysis showed that 39 of the initially uninfected partners had become infected. Genetic analysis showed that 28 of the infections came from the infected partner -- and 27 of these infections were from partners in the delayed-treatment group. The study was stopped, and everyone with HIV was offered treatment.