Why circumcision reduces HIV risk

January / February 2010 | Volume 9, Issue 1

Two men load five large bags of rice onto a donkey, dirt roads in the background
Photo by Yosef Hadar/The World Bank

Two key clinical trials in Africa led to findings
about how circumcision reduces HIV.

Most of the reduction in HIV acquisition attributed to male circumcision may be explained by the removal of foreskin tissue that contains HIV target cells. The decreased risk of HIV infection in circumcised men cannot be explained by a reduction in sores from conditions such as herpes, according to research published in PLoS Medicine.

Two key clinical trials in rural Uganda that led to this finding about HIV target cells were funded by the NIH's National Institute of Allergy and Infectious Diseases (NIAID), the Gates Foundation and Fogarty. Dr. Ronald Gray, a Fogarty grantee from the Johns Hopkins Bloomberg School of Public Health, and his colleagues' trials helped show that circumcision reduces the risk of male HIV infection by about 60 percent.

Researchers randomly assigned about 5,500 HIV-uninfected men to circumcision: some immediate and some in 24 months. At enrollment, they asked the men whether they had any symptoms of genital ulcer disease. The men were examined and tested over a course of two years.

Re-examining the data from these clinical trials, Gray and colleagues investigated infection with HSV-2, the virus that causes genital herpes, and whether genital ulcers of any cause, could account for the lower rates of HIV infection in the circumcised participants in the study.

The researchers found that reduction in symptomatic genital ulcer disease accounted for only about 10 percent of the protective effect associated with circumcision, and did not find any consistent role for HSV-2 in counteracting protection. They also suggest that circumcision reduces genital ulcer disease primarily by reducing the rate of ulceration due to causes other than herpes, including sores caused by mild trauma during intercourse.

The validity of some of the findings could be compromised because the further analysis was not specified in the original trial protocol. Nevertheless, the reduction of genital ulceration following circumcision seems to play only a minor part in the ability of male circumcision to reduce HIV acquisition in men.

The original research findings have had an effect: 90,000 men have been circumcised In Kenya since the government launched a national voluntary male circumcision drive in 2008, according to the AllAfrica news service.

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