The use of voluntary male circumcision to reduce the risk of HIV transmission in heterosexual men remains a highly contentious issue. While there is strong evidence that circumcised men are less vulnerable to HIV infection through heterosexual intercourse than non-circumcised men, the practice often evokes harsh criticism from either those who either disapprove of circumcision or question the validity of early research.
A series of randomized controlled trials conducted in Africa from 2005 to 2007 have shown that male circumcision can reduce the risk of vaginal-to-penile transmission by anywhere from 51% to 60%.
Based on the conclusiveness of these trials, the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) issued recommendations in 2007 stating:
"Male circumcision should be recognized as an additional, important strategy for prevention of heterosexually acquired HIV in men...(but) should never replace known methods of HIV prevention."
By 2011, more than 1.3 million voluntary medical male circumcisions had been performed, mainly in Eastern and Southern Africa where adult prevalence rates can run as high as 26%. President Obama further committed to support 4.7 million circumcisions by the end of 2013.
"Circumcision as Prevention" A One-Way Street?
On the flip side of the issue, much of the same research suggests that male circumcision does not provide the same protective benefit to an uninfected female partner in a serodiscordant relationship. There are several likely causes for this anomaly—including the inherent biological vulnerability of females and, in some instances, the premature resumption of sex before the circumcision wound was fully healed.
Neither is there evidence to suggest that circumcision will reduce the risk of infection in men who have sex with men (MSM), where the primary route of infection is anal sex. Whether circumcision can provide a protective benefit in men who engage in anal sex with a female partner remains equally inconclusive.
Further fueling debate is the fact that circumcisions do not appear to impact HIV transmission rates in developed countries as they do in generalized, high-prevalence populations like sub-Saharan Africa.
Based on the bulk of the evidence, the WHO/UNAIDS framed a strategic approach by stating:
"The greatest potential public health impact will be in settings where HIV is hyperendemic (HIV prevalence in the general population exceeds 15%), spread predominantly through heterosexual transmission, and where a substantial proportion of men (e.g. greater than 80%) are not circumcised."
In 2011, UNAIDS reported that the adult prevalence rate in sub-Saharan Africa was between 10% (in Malawi) and 26% (in Swaziland). By comparison, the adult prevalence rate in the U.S. hovers at around 0.6%.
Weighing the Evidence
Between 1989 and 2005, a number of observational studies in Africa noted the relationship between the percentage of circumcised men within a high-risk population and the lower rates of HIV infection. While some of the results were compelling—including a large cohort study in Uganda that showed the odds of infection were 42% less in circumcised men—there were nearly as many studies either contesting the results or questioning the author conclusions.
In 2005, a systematic review of 35 observational studies confirmed the association between increased circumcision rates and reduced female-to-male transmission rates. Still, the evidence was considered insufficient to warrant the use of circumcision as a population-based preventative tool.
From 2005 to 2007, a series of randomized controlled trials conducted in three African countries finally provided statistically relevant evidence in support of the practice.
- In Kenya, 2,784 men between the ages of 18 and 24 were recruited for a study led by the University of Illinois. The trial was terminated prematurely when circumcision was shown to have an efficacy of 53% in preventing HIV transmission.
- In South Africa, 3,273 men between 16 and 24 were enlisted in a trial funded by the Agence Nationale de Recherches sur la SIDA (ANRS). The trial was terminated after 17 months after interim results showed 60% fewer infections in the circumcised group.
- In Uganda, 4,996 men between 15 and 49 were recruited for a trial conducted by the John Hopkins Bloomberg School of Public Health. The trial was also terminated prematurely after demonstrating an efficacy of 51%.
While meta-analyses have largely supported the findings in the context of African epidemic, some have questioned whether implementation challenges—including reduced condom use and behavioral disinhibition—have yet to be fully addressed.
Possible Biological Mechanisms for Reduced Transmission
A number of studies in recent years have suggested that the bacterial biome beneath the foreskin may be the cause for the increased transmission risk in non-circumcised men. Research indicates that the dense bacterial population may turn the so-called Langerhans cells on the surface of the skin into "traitors" to their own immune defense.
Normally, Langerhans cells function by capturing and transporting invading microbes to the immune cells (including CD4 cells), where they are primed for neutralization. However, when the bacterial load increases, as happens beneath the foreskin, an inflammatory response occurs and the Langerhans cells actually infect the cells with the offending microbes rather than merely presenting them.
By circumcising the penis, the anaerobic bacteria beneath the foreskin are unable to thrive, thereby mitigating the inflammatory response. Further research may lead to the development of microbicidal agents or other non-surgical strategies to neutralize the effect.
Program Effectiveness in Africa
Mathematical modelling by WHO, UNAIDS and the South African Centre for Epidemiological Modelling and Analysis (SACEMA) suggests that, in a high-prevalence setting where heterosexual sex is the primary mode of transmission, one new infection would be averted for every five to 15 men newly circumcised. In theory, if 90% of men are circumcised within these populations, there could an associative reduction in female infections of around 35% to 40% (due to the lower community infection rates).
Cost-effectiveness analyses have shown that, by averting these infections, the burden on healthcare systems could be profoundly reduced. One study of the Gauteng Province in South Africa—where the infection rate is over 15%—showed that the cost of 1,000 male circumcisions (approximately $50,000) could produce a lifetime cost savings of over $3.5 million in antiretroviral medications alone, not to mention direct medical and/or hospitalization costs.
Still, some have argued that the calculations are overly optimistic, while one (widely debated) study asserts that the implementation of free condom programs are 95 times more cost-effective than circumcisions in averting HIV infection.
Is "Circumcision as Prevention" Viable in the U.S.?
From a public healthcare standpoint, it's important to note that no global body has ever recommended universal male circumcision as an HIV prevention option. Clearly, there are key differences in the dynamics of the African epidemic versus that of the developed world, particularly since over 60% of new infections in the U.S. are among men who have sex with men (MSM).
Additionally, the negative impact on women—already vulnerable due to biological and socioeconomic factors—is seen to outweigh any possible benefit of large-scale implementation, even in at-risk communities where heterosexual prevalence rates are high. Many believe that targeted messages around circumcision would have an disproportionately negative effect on communities where stigmatization already runs high and condom use consistently falls below 50%.
Nevertheless, a number of studies have shown that neonatal circumcision can reduce a U.S. male's lifetime risk of heterosexually acquired HIV by as much as 20%. In 2012, the American Academy of Pediatrics (AAP) issued an updated policy statement indicating that "the health benefits of newborn male circumcision outweigh the risks and that the procedure's benefits justify access to this procedure for families who choose it." Among the listed benefits were the prevention of urinary tract infections, penile cancer, and transmission of certain sexually transmitted infections, including HIV.
Most doctors and health authorities take a non-biased position in regards to elective adult male circumcision, stressing that it decreases rather than eliminates the risk of vaginal-penile transmission of HIV. There are currently no recommendations in the U.S. for the use of voluntary male circumcision to reduce transmission risk in men.
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