Does circumcision reduce HIV risk?

Question

I've seen numerous claims that circumcision reduces HIV risk, both on TV and online.

Have there been any studies to verify if circumcision does or doesn't reduce HIV risk in a statistically-significant manner?

Answer 1

I would have to respectfully disagree with Russell's answer and say: No. Circumcision does not reduce HIV risk.

The three controlled intervention trials suffer from some VERY major design flaws, which cast more than a reasonable doubt about the supposed 'benefit' of circumcision in males.

A Cochrane review of circumcision questions the validity of previously performed studies on circumcision for the following reasons:

• Performance bias
• Attrition bias
• Selection bias

They identified 14 cross sectional studies with inconsistent findings - 4 were statistically significant for a benefit to circumcision, 2 were statistically significant for harm from circumcision. They also mentioned study heterogeneity.

They summarize with (bolded emphasis mine):

In assessing the quality of the observational studies we identified 10 potentially important confounders that studies would need to ensure were either balanced between circumcised and uncircumcised groups or, if unbalanced, that were adequately adjusted for (see Box 2).

Many studies either did not measure these variables or, if reported, were either not balanced between groups or not adjusted for.

It is important to note that observational studies, unlike RCTs, can only adjust for known confounders, and only then if they are measured without error. The effect of unknown confounders may well be operating in either direction within and across all of the included studies.

The studies from high-risk groups included in this review do report a powerful protective effect of circumcision, measured by both unadjusted and adjusted odds ratios. More mixed results were reported for the general population. As all the observed results could be explained by likely confounding, RCTs are essential before circumcision is implemented as a public health intervention. Implementation of circumcision will encounter cost, both financial and in terms of potential personal harm; no adverse effects are reported in this review only because none of the observational studies investigated them. Feasibility issues of implementation are beyond the scope of this review but need to be carefully considered.

If those clinical trials in Africa are flawed, how can one justify using them as the basis for a policy?

There is a real risk of risk compensation reducing the 'benefit' of circumcision.

The various pro-circumcision studies all cite the need for 'other' forms of prevention, ie. condoms - which in Africa aren't as available (or used) as they are elsewhere in the world.

Further Reading:

• Circumcision status and HIV infection among MSM: Reanalysis of VAXGen VAX004 HIV vaccine clinical trial data, with conclusion: "Among men who reported unprotected insertive anal sex with HIV-positive partners, being uncircumcised did not confer a statistically significant increase in HIV infection risk. Additional studies with more incident HIV infections or that include a larger proportion of uncircumcised men may provide a more definitive result."
• Circumcision status and HIV/STI amongst MSM: Study with conclusion "Our findings suggest that male circumcision would not be likely to have a significant impact on HIV or sexually transmitted infections acquisition among MSM in Seattle."
• Study of male to female transmission (By the same researcher that produced the Uganda RCT!). An RCT (aborted early due to "futility") with conclusion: "Circumcision of HIV-infected men did not reduce HIV transmission to female partners over 24 months; longer-term effects could not be assessed."
• Case-Controlled Study of US Navy Men with conclusion: "[male circumcision] is not associated with HIV or STI prevention in this U.S. military population."
• Neonatal Circumcision does not reduce HIV/AIDS
• CDC Fact Sheet: Male Circumcision and Risk for HIV Transmission and Other Health Conditions: Implications for the United States, as cited by Russell. As mentioned above, this is countered by the Cochrane study.
• The above fact sheet cites this source (#1), but that was debunked above.
• The above fact sheet cites this source (#3) re: foreskin tearing aiding HIV infection. This is discussed here and an alternative solution has been proposed.
• The above fact sheet cites this source (#4), which is countered here, where it is determined to be "unlikely to have a substantial public health impact in reducing acquisition of most STIs in homosexual men"here
• This Lab Study suggested that "Circumcision likely reduces risk of HIV-1 acquisition in men by decreasing HIV-1 target cells", but is countered by this letter.

I'll be happy to counter the other sources at a later point, it's 10:30 pm here and I'm knee deep in setting OEL limits.

Answer 2

My own answer ripped straight from this question:

The CDC concludes that circumcision does reduce risk of disease based on multiple lab studies and controlled intervention trials, in addition to the statistical research that opponents focus on for "refuting" the evidence.

This is a topic where research has been done and confirmed, it boils down to this:

Research indicates reduced HIV risk for circumcised men, both in labs and in the real world (where people don't always wear condoms, for whatever reason).

References:

• ANRS 1265 Trial, with the conclusion: "Male circumcision provides a degree of protection against acquiring HIV infection, equivalent to what a vaccine of high efficacy would have achieved. Male circumcision may provide an important way of reducing the spread of HIV infection in sub-Saharan Africa."
• Male circumcision for the prevention of heterosexually acquired HIV infection: a meta-analysis of randomized trials involving 11 050 men. A meta-analysis concluding that the studies are valid. In particular, it concluded that "Male circumcision is an effective strategy for reducing new male HIV infections. Its impact on a population level will require consistently safe sexual practices to maintain the protective benefit."
• Further meta-analysis concluding causal link
• WHO statement: "Male circumcision reduces the risk of becoming infected with HIV, but does not provide complete protection" (well of course it's not complete protection...)

Basically every significant health organization in the world is behind this, entailing almost 40 different clinical trials since the 1980s and numerous lab trials demonstrating that the uncut penile tissue around an intact foreskin is more receptive to HIV infection.

Also of note, this only speaks to the risk to the male in question. It also may not apply to subsets (for any medical research you will always be able to find some subgroup of the population that has a different outcome)

Thanks to @OddThinking it appears another real world trial has been performed supporting this claim. This study directly provides real evidence against the risk compensation claim.

Three years after the voluntary medical male circumcision (MC) campaign rolled out in the Orange Farm Township in South Africa, the first “real world” results are available showing a marked reduction of HIV acquisition among circumcised adult men with a 55 percent lower HIV prevalence (proportion of HIV-infected people) among circumcised men compared to their uncircumcised counterparts and overall reduction in HIV incidence (the number of new cases) among men 15 to 34 years old of 76 percent.