New Delhi: HIV-infected people with relatively healthier immune systems can dramatically reduce the transmission of the virus to their sexual partners if they are treated immediately with oral antiretroviral drugs, says a large-scale clinical study.
The US National Institutes for Health (NIH) trial, known as HPTN 052, found antiretroviral treatment to be 96 per cent effective in reducing sexual transmission of HIV.
The results are the first from a major randomized clinical trial to indicate that treating an HIV-infected individual can reduce the risk of sexual transmission of HIV to an uninfected partner.
Preliminary results of the trial were so convincing that the study, scheduled to end in 2015, was halted early.
"Previous data about the potential value of antiretrovirals in making HIV-infected individuals less infectious to their sexual partners came largely from observational and epidemiological studies," said NIAID Director Anthony S. Fauci.
"This new finding convincingly demonstrates that treating the infected individual-and doing so sooner rather than later-can have a major impact on reducing HIV transmission," he added.
Led by study chair Myron Cohen, director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill, the trial began in April 2005 and enrolled 1,763 couples, all at least 18 years of age.
"Because 97 per cent of the couples were heterosexual, it`s unclear whether the results can be extrapolated to men who have sex with men," researchers said.
The study was conducted at 13 sites in Botswana, Brazil, India, Kenya, Malawi, South Africa, Thailand, the United States and Zimbabwe.
HIV-infected partners were randomly assigned to one of two groups: those who received antiretroviral drugs immediately after joining the study and those whose treatment was deferred until their CD4 count - a measure of the immune system`s ability to fight infection - fell below 250 or they had an AIDS-related event.
Throughout the study, both groups received the same amount of HIV-related care that included counseling on safe sex practices, free condoms, treatment for sexually transmitted infections, regular HIV testing, and frequent evaluation and treatment for any complications related to HIV infection.
In its review, the researchers found a total of 39 cases of HIV infection among the previously uninfected partners.
Of those, 28 were linked through genetic analysis to the HIV-infected partner as the source of infection.
Seven infections were not linked to the HIV-infected partner, and four infections are still undergoing analysis. Of the 28 linked infections, 27 infections occurred among the 877 couples in which the HIV-infected partner did not begin antiretroviral therapy immediately. Only one case of HIV infection occurred among those couples where the HIV-infected partner began immediate antiretroviral therapy.
The researchers also found that HIV-infected partners who received immediate treatment were less likely to develop extrapulmonary tuberculosis.