18 December 2009 

Circumcision and its potential impact on the spread of HIV among gay and bisexual men

In several high-income countries gay and bisexual men are disproportionately affected by HIV infection and other sexually transmitted infections such as syphilis. What's more, data from HIV test results suggest that since 2001 HIV infections in the following countries are increasing among men who have sex with men:

  • Canada 
  • Australia
  • France
  • Germany
  • Netherlands
  • United Kingdom
  • United States

Even if the number of new HIV infections was to remain stable each year, American statistical projections suggest that a large proportion of gay and bisexual men are likely to become HIV positive over the next 20 years in that country.

In light of the resurgence of HIV infections, researchers and health policy planners in high-income countries are assessing different opportunities for interventions that might have an impact on the HIV pandemic in these countries. One such possibility is male circumcision.

In parts of the world where HIV is relatively common, such as in southern Africa, three randomized controlled trials in heterosexual men have found that male circumcision reduces the risk of these men becoming infected by their female partners by about 60%.

For this reduction in risk to be sustained, circumcised men in southern Africa will need to use condoms. And long-term monitoring of circumcised men is needed to confirm that circumcision can protect them for many years. Nevertheless, some researchers in high-income countries suspect that circumcision of gay and bisexual men might have a role to play in reducing HIV transmission in these communities.

In this CATIE News bulletin, we review recent evidence about the possible impact of male circumcision in gay and bisexual men in high-income countries.

Australia—circumcision study

Researchers in Australia have been conducting several studies to assess the impact of circumcision on HIV transmission. In one study, they recruited 1,426 HIV-negative participants, 66% of whom were circumcised. Of the 1,426 men, 95% identified as gay and 5% were bisexual. Participants were monitored for up to four years, to June 2007.

During the study, 53 men became HIV positive. Taking into account the presence of sexually transmitted infections (STIs), such as anal gonorrhea and warts, the researchers found that, overall, circumcision did not offer any statistically significant protection from HIV for these men.

The Australian team also questioned study participants about their roles during sex, such as whether they performed insertive or receptive anal sex, and here's what they found:

  • There were seven new HIV infections among men who said that they "preferred" the insertive role for anal sex;
  • There were 12 new HIV infections among men who said that they "preferred" the receptive role for anal sex;

Among men who preferred the insertive role for anal sex, being circumcised was associated with a small but statistically significant reduction in the risk of becoming HIV positive.

Caution and concerns

There are several reasons to be cautious when assessing the data from this Australian study, including the following:

  1. This was an observational, or cohort, study. By its nature, such a study can only find associations; it cannot prove a relationship between cause (such as circumcision) and effect (possible protection from HIV infection). At most, the Australian results are interesting; however, they need to be confirmed in a more robustly designed study, such as a randomized controlled trial.
  2. Though researchers found that 30% of men "consistently reported a preference for the insertive role in anal intercourse," only 10% of participants in this study reported that they were 100% exclusively insertive when practicing anal intercourse. This difference between 30% of men claiming that they preferred a certain role and only 10% of men consistently practicing that role should give readers and researchers pause for thought. This means that, at best, only about 10% of gay and bisexual men might benefit from circumcision.

Putting their findings into perspective, the Australian team made this statement: "As a minority of HIV infections [in this study] occurred in those reporting no unprotected anal intercourse, circumcision is unlikely to have a major impact on HIV incidence in homosexual men in Australia."

A meta-analysis

In 2008, researchers in the United States published their systematic review of 15 observational studies—a meta-analysis—to examine the possible impact of circumcision on HIV transmission among gay and bisexual men.

These researchers reviewed data collected on 53,567 men, 52% of whom were circumcised. The studies they reviewed took place between 1989 and 2007, mostly in high-income countries.

The study team found that, overall, circumcision was associated with a 15% reduction in the risk of becoming HIV positive. However, this reduction in risk was not statistically significant.

In three of the 15 studies assessed, there was sufficient information about circumcision status and whether men engaged primarily or exclusively in insertive anal sex. In analysing these three studies, which contained data on 2,238 men, the researchers found that, again, circumcision was not associated with any statistically significant protection from HIV.

Seven of the 15 studies used in the meta-analysis were able to provide sufficient information about STIs (other than HIV) in 15,233 circumcised men and 11,003 uncircumcised men. An analysis of these studies found that circumcision did not provide any statistically significant protection from STIs.

Meta-analysis—before the time of HAART

When researchers examined studies done before 1996, when highly active antiretroviral therapy (HAART) became available in high-income countries, they found that circumcision was associated with a 53% reduction in the risk of becoming HIV positive. What's more, this reduction in risk was statistically significant. Why was this protective effect not seen after 1996? The study team highlights other research that confirms a surge in unprotected anal sex among gay and bisexual men after that year, which has resulted in increased STIs and HIV infections. It is important to note that the increase in risk behaviour has overwhelmed any protective effect that circumcision might have had in these men.

A CDC analysis of circumcision data

A research team at the U.S. Centers for Disease Control and Prevention (CDC) reanalyzed data collected from a randomized placebo-controlled trial of an HIV vaccine, trial VAX 004. This vaccine study was done between 1998 and 2002. The CDC reanalysis used data collected from 4,889 men, 86% of whom were circumcised. Here are some key findings:

  • Of the 4,889 men, about 7% (323 men) became infected over the course of the study. Of these infected men, 87% were circumcised.
  • Being uncircumcised did not confer any increased risk for HIV infection among men who had insertive anal intercourse.

It is noteworthy that the CDC team also found that having unprotected anal intercourse—either insertive or receptive—was linked to an increased risk of becoming HIV positive.

The CDC reanalysis raises doubts about any protective effect of what is being called "strategic positioning"—that is, the HIV-negative man being the insertive partner (or “top”) during sex—regardless of circumcision status.

Australia—a mathematical model

Researchers in Australia created a mathematical model to simulate the impact that circumcision might have on the HIV epidemic among gay and bisexual men. The researchers found that the circumcision of these men was likely to confer some protection against HIV infection. However, they assumed that the protective effect of circumcision would be similar to that seen in heterosexual men in southern Africa—about 60%. There is no evidence from any prospective randomized study that circumcision would have a similar protective impact on gay men. What's more, the aforementioned meta-analysis and CDC reanalysis suggest that circumcision does not offer any significant protection from HIV. Therefore, the Australian group's assumption of a 60% protective effect from circumcision seems highly optimistic.

Even with such optimistic modeling, the Australian researchers found that the protective effect of circumcision would be relatively small and could be reversed if just a small proportion (10%) of circumcised gay men engaged in unprotected anal sex. Indeed, looking at their model's prediction over 25 years, the Australian researchers stated that the impact of circumcision would not “substantially” change the number of infected gay and bisexual men. This finding from a mathematical model is striking but perhaps speaks to the weak, if any, impact that circumcision would have on sexually active gay and bisexual men.

The current and future epidemic

HIV is spreading via unprotected sex in high-income countries, particularly among gay and bisexual men. In fact, in some gay and bisexual communities in North America and Western Europe, the proportion of men with HIV is high, similar to that seen in some countries in sub-Saharan Africa. How is this possible?

There are a number of factors that likely play a role in the current spread of HIV in high-income countries among gay and bisexual men, as follows:

  • There are growing reports of gay and bisexual men engaging in unprotected anal intercourse.
  • HIV infection may now be perceived by some people as a less serious illness than it was before the availability of HAART.
  • Some HIV-negative men believe that their personal risk of getting HIV has been reduced.
  • Some HIV-positive men hold the incorrect assumption that having a low or undetectable level of HIV in the blood means that virus levels are also low in the semen—and that therefore they can have unprotected sex without risk of infecting another person.
  • Increased and sustained outbreaks of sexually transmitted infections among gay and bisexual men are occurring. STIs can increase the risk of HIV transmission.

Researchers studying the increase and spread of HIV have concluded in several studies that increases in high-risk sex have overwhelmed any decrease in infectivity due to HAART. This does not mean that current HIV prevention efforts have failed—without these efforts, rates of new cases of HIV and STIs might be much higher. This environment of high-risk sex and STIs must be taken into account when considering the potential impact and rollout of new prevention interventions—such as male circumcision, microbicides or pre-exposure prophylaxis (PrEP)—in gay and bisexual men in high-income countries.


Additionally, policy planners and researchers should note that the physiology of the vagina is different from that of the anus. When sexually aroused, most women's vaginas secrete fluid that provides lubrication during sex. There is no analogous natural increase in lubrication for the anus among sexually aroused men. This may partially explain why unprotected anal sex between men has always been associated with a greater risk for HIV transmission for both insertive and receptive partners when compared to heterosexual intercourse.


Unlike heterosexual men, gay and bisexual men tend to engage in sexual roles that are fluid. That is, sometimes these men practice insertive anal sex, and sometimes they practice receptive anal sex, and sometimes both. In common parlance, these men describe themselves as "versatile" rather than "tops" or "bottoms." This fluidity of sexual role-playing means that interventions that may work for heterosexual men or women may not work for most gay and bisexual men.

The emergence of HIV

High rates of circumcision in North American in the early 1980s did not prevent the appearance or expansion of the HIV epidemic in this continent.

Taking all of these points into consideration, circumcision, over the long term, is unlikely to have any significant impact on the spread of HIV among gay and bisexual men in high-income countries.

—Sean R. Hosein


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