"While we found that antiretroviral use alone may account for a 60 percent reduction in risk of HIV transmission, a concurrent increase in risk behavior meant that rates of new infections did not decline sharply, but remained roughly stable for the period studied," said study lead investigator Travis Porco, PhD, MPH, an epidemiologist with SFDPH at the time the study was conducted.
The study, to be published in the January 2, 2004 issue of AIDS, analyzed data from 1994 to 1999 from the San Francisco Young Men's Health Study (YMHS), which followed young gay men who were initially uninfected with HIV. Participants were asked about their sexual practices and tested for HIV at four follow-up visits, which included two before the widespread introduction of HAART for people with HIV in San Francisco and two later visits.
The study estimated the chances that a HIV-uninfected person would become infected by a sexual partner after factoring in sexual practice and condom use. Researchers found a per partnership decline of 60 percent in risk of becoming infected that occurred following the introduction and the widespread use of HAART by HIV-infected persons in San Francisco.
"Unfortunately, the doubling of the rate of unprotected receptive anal intercourse by study participants offset the beneficial effects of antiretroviral treatments becoming widely available," said study co-author and YMHS lead investigator, Dennis Osmond, PhD, UCSF professor in the Department of Epidemiology and Biostatistics.
"While our findings confirm that treatment of HIV-infected individuals can have quite a significant impact on the spread of AIDS, they also show that treatment needs to be accompanied by prevention interventions to reduce risky behavior in order to see the benefit in reduced rates of new HIV infections in the community," said Osmond.
Porco is currently senior epidemiologist with the Surveillance and Epidemiology Section of the Tuberculosis Control Branch of the California Department of Health Services. Other co-authors of the study are Jeffrey N. Martin, MD, MPH, assistant professor in the UCSF Department of Epidemiology and Biostatistics; Kimberly Page Shafer, PhD, MPH, assistant professor of medicine at the UCSF Center for AIDS Prevention Studies; Amber Cheng, MPH, statistician in the UCSF Department of Epidemiology and Biostatistics; Edwin Charlebois, PhD, MPH, assistant professor of medicine at the AIDS Policy Research Center at the UCSF AIDS Research Institute; and Robert M. Grant, MD, MPH, assistant investigator at the Gladstone Institute for Virology and Immunology and UCSF assistant professor of medicine.
The study was funded by grants from the National Institute on Drug Abuse, the National Cancer Institute, the National Institute of Dental and Craniofacial Research (all parts of the National Institutes of Health), the University-Wide AIDS Research Program of the State of California, the AIDS Clinical Research Center of the University of California, and the UCSF/Gladstone Institute for Virology and Immunology Center for AIDS Research.
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