Circumcision helps protect heterosexual men against genital herpes and a virus that causes genital warts and cancer but has no effect on the bacteria that causes syphilis, two trials in Uganda show.
The study in Wednesday's New England Journal of Medicine builds on earlier research that found circumcision reduces a man's risk of HIV infection by more than 50 per cent.
"Medically supervised adult male circumcision is a scientifically proven method for reducing a man's risk of acquiring HIV infection through heterosexual intercourse," said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Disease, which funded the study.
"This new research provides compelling evidence that circumcision can provide some protection against genital herpes and human papillomavirus infections as well."
The latest data showed a 25 per cent reduction in herpes and a 34 per cent reduction in the prevalence of HPV among participants.
The 3,393 men were aged 15 to 49 and initially tested negative for both HIV and herpes simplex virus type 2, which causes genital herpes.
A control group of 1,709 men received medical circumcision after a delay of 24 months. All participants were followed for herpes and syphilis infection for two years.
In an editorial that accompanied the study, Dr. Matthew Golden of the University of Washington called for circumcision to be made widely available in North America.
"For most parents, the default should be circumcision," said Golden. "Obviously, these are complex decisions, and parents have to do what they think is right for their children, but there are significant health benefits."
Canadian pediatricians weigh evidence
Circumcision rates have been plummeting in Canada since the 1970s, when the Canadian Pediatric Society recommended against routinely performing the procedure.
The society has been reviewing that recommendation, and officials said the new study will be included in the review.
"This certainly provides new information that would tip the scale to say there may be quite relevant medical information that would demonstrate that there was a benefit that previously wasn't appreciated," said Dr. Robert Bortolussi of the Canadian Pediatric Society in Halifax.
If circumcision does become a recommended procedure, it could take time before it becomes widely available — partly because many doctors were never taught how to do it, Bortolussi said.
The human papillomavirus, or HPV, is the most common sexually transmitted infection in the world. It causes cervical cancer, which kills 300,000 women globally every year, and anal and penile cancers.
The World Health Organization and the United Nations' program on HIV/AIDS have promoted circumcision since 2007 for reducing the risk of AIDS in areas where heterosexual transmission is high.