Studies in the developed world

Would circumcising men benefit some populations in developed countries or countries without generalised epidemics? In many countries with highly focal epidemics, the answer is probably not, if most infections are among injecting drug users or gay men (see below for the evidence on gay men).

However circumcision might help to reduce HIV incidence and prevalence if there is significant heterosexual transmission amongst certain population groups – say, between female sex workers and their clients, or amongst specific high-risk ethnic or cultural minorities.

One review of evidence from the USA,¹ where HIV disproportionately affects the black and to a lesser extent the Latino population suggests that circumcision could cut the risk of heterosexual HIV transmission in black and Hispanic men.

Based on the African data the authors from the CDC said that "it is likely that circumcision will decrease the probability of a man acquiring HIV via penile-vaginal sex with an HIV-infected woman in the US."  Nonetheless because there are many differences between the underlying HIV epidemics in Africa and the US, the impact of adult male circumcision on HIV transmission rates in the US was hard to predict.

Adult male circumcision would most likely have the largest impact in populations where circumcision has been rare. Although circumcision is already very common in the US, circumcision rates have traditionally been lower among Hispanic men in the United States, where only 42% of Mexican-American men are circumcised, compared with 88% of non-Hispanic white men and 73% of non-Hispanic black men.

The authors highlight findings from a study of men attending a Baltimore STI clinic,² which found that while circumcision was not associated with a protective effect throughout the whole clinic population, it was associated with a reduced risk of infection among men known to have had unprotected sexual intercourse with HIV-positive female partners. The risk reduction was approximately 55%, although the confidence intervals of this estimate were wide (0.22–0.97).

"Some sexually active men may consider circumcision as an additional HIV prevention measure, but should do so only in consultation with their physician or health care provider, and with a clear understanding of the costs and risks of circumcision," comments the CDC.

Men who choose to be circumcised should be counselled about the importance of waiting until wound healing is complete before having sexual intercourse.

Most of the evidence suggests that circumcision is unlikely to reduce HIV transmission between gay men. This is not unexpected, as more HIV is likely to be acquired rectally than via the penis, but there is little evidence that even ‘tops’ who exclusively practise insertive sex (or claim to) are likely to benefit as a group, though there could be benefit on an individual level.

The HIV Network for Prevention Trials Vaccine Preparedness Study enrolled 3257 gay men in six US cities from 1995 to 1997.³ This was a longitudinal study, and HIV incidence was 1.55 per 100 person-years over 18 months of follow-up. Men who were not circumcised were twice as likely to acquire HIV as men who were. However this was not a randomised controlled trial and although the results were suggestive, they could not rule out differences in behaviour between circumcised and uncircumcised men as the cause.

One 2001 study⁴ explored the relationship between circumcision and HIV transmission in gay men in Sydney, Australia. Between 1993 and 1999 74 gay men were interviewed soon after being diagnosed with recent infection. The men were asked to describe the behaviour they thought most likely to have given them HIV; infection assumed to be through unprotected insertive sex comprised 15% of all infections. The researchers found no association between circumcision status and infection by insertive unprotected anal intercourse.

Another Australian study suggests that circumcision does not alter HIV incidence in gay men.⁵ The study looked at circumcision status and HIV seroconversion in the Health in Men (HIM) cohort of 1427 initially HIV-negative homosexual men recruited between 2001 and 2004. At enrolment, 66% of cohort participants were circumcised. In 2006, there were 49 seroconversions among cohort participants: 29 (69%) in circumcised men and 13 in uncircumcised men, representing an incidence of 0.80 per 100 patient years. There was no difference in the incidence of HIV infection between circumcised and uncircumcised men. This remained true when the analysis controlled for age, anorectal STIs, and insertive or receptive unprotected anal intercourse (UAI) with someone who was HIV-positive.

Among the men who reported not having receptive UAI, there were nine seroconversions, but there was no difference in the risk of HIV infection between circumcised and uncircumcised men.

The researchers conclude: “Although statistical power was limited, among men who were more likely to acquire through insertive UAI, there was no relationship [between circumcision and HIV seroconversion]. As most HIV infections in homosexual men occur after receptive anal sex, circumcision is unlikely to be an effective HIV prevention intervention in Australian gay men.”

Another 2007 study from the United States⁶ interviewed 1079 black and 957 Latino MSM in New York, Philadelphia, and Los Angeles. They found that 74% of black MSM were circumcised and 33% of Latino MSM.

There was no statistically significant association between circumcision and HIV status among Latino MSM (adjusted odds ratio [AOR] = 1.10, 95% confidence interval [CI]: 0.73 to 1.67) or black MSM (AOR = 1.23, 95% CI: 0.87 to 1.74).  Further, there was no evidence that circumcision was protective among men who had only engaged in unprotected insertive anal sex.