Circumcision significantly lowers HIV risk in men, study finds

Circumcision reduces the risk of HIV infection in men by half, according to a study conducted among nearly 8,000 men in Kenya and Uganda, researchers reported Wednesday.

Circumcision proved so effective that the study was halted a year early and the procedure was offered to all study participants.

The findings, which apply only to heterosexual transmission of HIV from women to men, will have less impact in the United States, where nearly 80 percent of males are circumcised and sex among gays plays a major role in transmission of the virus.

But they could have a major effect in the rest of the world, where heterosexual contact is the major form of transmission.

Previous research has suggested circumcision is beneficial, but the new trial is "definitive," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which co-sponsored the study with the Canadian Institutes of Health Research.

"It's not a magic bullet," said Dr. Kevin De Cock, director of the World Health Organization's (WHO) Department of HIV/AIDS, but it has the potential to prevent "many hundreds of thousands, and perhaps millions, of infections over coming years."

Nonetheless, experts cautioned against the possible misperception that circumcision eliminates risk. The procedure "has to be integrated with all the other things that we do to prevent new HIV infections," said epidemiologist Robert Bailey, of the University of Illinois at Chicago, who led the Kenya part of the study.

Circumcision rates vary widely in Africa. The average rate is just more than 60 percent for the entire continent but less than 20 percent in South Africa, where the AIDS epidemic is at its most severe. HIV causes AIDS.

Early small trials of circumcision had shown a beneficial effect from the procedure, a 25- to 30-minute surgery in which the foreskin is removed from the penis, but experts feared that the benefits might be related to cultural biases rather than the procedure.

Even a 2005 study of more than 3,000 men in South Africa, which showed circumcision reduced HIV transmission by 60 percent, failed to move funding agencies, which feared the findings could not be reproduced at other sites.

In August, Bill Gates and former President Clinton urged an AIDS conference in Toronto to watch the research on circumcision closely. Gates, who controls the Bill & Melinda Gates Foundation, called circumcisions as an AIDS preventive "promising" and "exciting." But both men cautioned that logistics of mass circumcisions in Africa would impede the procedure's usefulness in eliminating the disease.

The new study results appear to have tipped the balance. UNAIDS and the WHO said they would convene a panel of experts to determine how to implement the findings.

The Ugandan study enrolled 4,996 men between 15 and 49, half of whom underwent circumcision. All the men in both studies also received counseling on HIV-risk reduction and were advised to wear condoms.

But because condom use is not 100 percent, the researchers expected to see infections in both groups.

A National Institutes of Health data-monitoring board reviewed the data Tuesday and found 43 cases of HIV infection among the uncircumcised men, compared with 22 among the circumcised, a 48 percent reduction in risk.

The Kenyan study enrolled 2,784 men between 18 and 24. The monitoring board found 47 cases of HIV among the uncircumcised men, compared with 22 among the circumcised, a 53 percent reduction in risk.

Faced with those results, the board said the trial should be terminated immediately. "Circumcision is now a proven, effective prevention strategy to reduce HIV infections in men," Bailey said

About 1.7 percent of the circumcised men suffered mild side effects, mostly bleeding and infections. That is about the same rate that occurs among infants undergoing circumcision in the United States, Bailey said.

A trial in Africa is studying whether circumcision of men will reduce the HIV-infection rate among women. The results will not be available until 2007.

Researchers have speculated about the potential biological mechanism by which the procedure reduces infections.

Fauci said during a Wednesday teleconference that cells of the foreskin appear to be more fragile than those on the rest of the penis, and thus are more susceptible to invasion by HIV.

The folds of the uncircumcised penis can trap the virus, holding it against the penis for a longer time in a warm, moist environment that promotes infection.

Material from The Seattle Times archive is included in this report.