Circumcision will halve HIV rates but may take decades to reach full impact

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Tripling the rate of male circumcision in a country with a current circumcision rate of 25% and a high rate of heterosexually-acquired HIV will eventually halve HIV incidence, a mathematical model by Richard White of the London School of Hygiene and Tropical Medicine has shown.

However it would take 50 years for that 75% rate of circumcision to reach full effectiveness, and it would require circumcision of the majority of sexually-active adult men (aged 15-45) rather than, as recommended by the World Health Organization, males aged 12-30, if it were to be as effective as is possible. It was shown that circumcision would immediately result in money being saved, however, as the cost per HIV infection averted would always be lower than the cost of providing care if that infection had not been averted.

White was in Mexico City presenting data from a mathematical model of the efficacy of a national circumcision programme to the XVII International AIDS Conference. Alongside White’s presentation:


voluntary male medical circumcision (VMMC)

The surgical removal of the foreskin of the penis (the retractable fold of tissue that covers the head of the penis) to reduce the risk of HIV infection in men.


The surgical removal of the foreskin of the penis (the retractable fold of tissue that covers the head of the penis) to reduce the risk of HIV infection in men.

mathematical models

A range of complex mathematical techniques which aim to simulate a sequence of likely future events, in order to estimate the impact of a health intervention or the spread of an infection.

randomised controlled trial (RCT)

The most reliable type of clinical trial. In a trial comparing drug A with drug B, patients are split into two groups, with one group receiving drug A and the other drug B. After a number of weeks or months, the outcomes of each group are compared.

control group

A group of participants in a trial who receive standard treatment, or no treatment at all, rather than the experimental treatment which is being tested. Also known as a control arm.

  • Nicolai Lohse of UNAIDS presented a synthesis of the many recent models of the effect of circumcision, showing that there would be fewer HIV infections in men even if condom use shrank to nothing, and women would benefit as long as condom use did not fall by more than two-thirds;
  • Frederick Sawe of the Kenya Medical Research Institute reported on how HIV prevention messages were being rapidly integrated into traditional circumcision ceremonies;
  • John N Krieger of the University of Washington, Seattle, reported that men circumcised in a Kenyan randomised controlled study had no higher rates of sexual dysfunction than uncircumcised controls and reported more sexual pleasure post-circumcision; and
  • Bertran Auvert of the French health research agency INSERM reported that two-thirds of men in the township where the first randomised controlled trial (RCT) of circumcision was carried out, Orange Farm near Johannesburg, would be willing to be circumcised. But he also found that a large minority of men who said they had been ‘circumcised’ had in fact not been, due to confusion between circumcision and other forms of initiation ceremony for adolescents.

The long-term effect of circumcision

Richard White’s model took a baseline population where HIV prevalence was 18% in men and 25% in women, where HIV prevalence peaked at around 28 in women and 34 in men, and where 25% of the men were already circumcised, and then examined the effect over the next half-century of a national programme that tripled the male circumcision rate to 75%. He also looked at what would happen if only HIV-negative men were circumcised, or if HIV-positive men were included, whether circumcision also reduced male-to-female HIV transmission. The model also looked at the effect of different combinations of sexually transmitted infections (STIs) in the population, and what would happen if men had sex before their circumcision wound healed.

He found that there would be an immediate reduction of 8.1% in HIV incidence the second year after circumcision. After ten years incidence would have gone down by nearly a quarter, but it would take 50 years for circumcision alone (ignoring the effect of any other prevention measures or of HIV treatment) to halve male incidence.

Incidence in women would decline more slowly than in men, going down by only about 12% after 10 years, but would catch up as the effect of circumcision spread into the general population, and incidence would have declined by 44% after 50 years.

Fewer than three HIV infections per 100 circumcision operations would be avoided in the first two years after circumcision rose to 75% coverage, but by 30 years after mass circumcision there would be nearly one HIV infection avoided for every two circumcisions.

The cost of averting one HIV infection, for the base scenario in which 15-45 year olds were circumcised, would be $1806 in the first two years, but would decline to only $200 by the time the programme had been running for 20 years. However this compares with a cost of over $4000 for treating the infection that would otherwise have happened, so circumcision is cost-saving from the start if performed on adult men.

If circumcisions were performed on boys under 15, before the age of first sex, these effects on HIV incidence would be delayed by 20 years and if performed on babies only, the effects would be delayed by 40 years, as it is much more effective initially to circumcise men at the time they are most vulnerable to HIV.

Including HIV-positive men in a national circumcision programme would make very little difference to incidence reductions, White said, as would the subsequent rate of STIs in the circumcised population (with about 5% of the decline in incidence being due to circumcision reducing herpes infections, rather than a direct effect on HIV incidence).

However large-scale behavioural change would have an effect. In his model, if 40% condom use in casual and commercial sex declined to 20% (condom use in steady relationships was assumed to be zero), it would wipe out the benefits of circumcision.

Nicolai Lohse said that so many mathematical models of the effect of circumcision had appeared in scientific literature in the last three years, including three others in addition to White’s at this conference, that UNAIDS had called a series of three technical meetings to look at the best choice of model and how well they fitted observed data.

In the end a high level of agreement over the main findings was found among the models. Most models came out with circumcision producing a reduction of around 60% in the risk of HIV acquisition for men who had the operation. The risk to women of acquiring HIV would be also reduced if men were circumcised, as there would be fewer HIV-positive men in the population. The risk to women of HIV acquisition would decline by 2% if only 5% of men were circumcised, by 20% if 50% of men were circumcised, and by 38% if 95% were circumcised.

Lohse said that most models were more optimistic than White’s about the effect of ‘condom migration’ on HIV incidence. His synthesis of the models indicated that the risk to women of acquiring HIV would only rise above baseline levels if condom use in men fell by more than two-thirds, while men would benefit from circumcision even if they stopped using condoms altogether.

Traditional circumcision

Frederick Sawe presented a study at the Toronto World AIDS Conference two years ago, about Luo men coming forward voluntarily for circumcision in the tea-planting district of Kericho in Kenya, where they are the only tribal group who are not traditionally circumcised.

This year he presented the results of a study that assessed the feasibility and acceptability of integrating a) modern medical safety standards and b) HIV and sexual health information into the traditional circumcision ceremonies performed by the other local ethnic groups.

Boys in these groups are traditionally circumcised when they reach the age of 11-15. For the ceremonies they wear sheepskin costumes, straw headdresses and whitened faces, and after the circumcision they enter a one-month period of seclusion in the bush during which they are instructed in tribal rules and norms by a mentor, usually a relative.

The study worked with a group of trainers who in turn provided training for 222 of these mentors alongside 70 of the boys’ parents and others, including provincial administrators and church leaders. Altogether the programme reached 1345 adolescent boys. Forty-five traditional circumcisers (the men who actually wield the knife, equivalent to the mohel in Judaism) were also trained, of whom 58% had had some degree of medical training, largely as nurses or operating assistants. In the end 72% of circumcisions were performed by a person with some medical training. Sawe commented that “a transition from a traditional to a pseudo-traditional/medical approach seems to be happening in Kenya’s southern Rift Valley Province.”

Sexual function and pleasure unaffected by circumcision

John Krieger studied the effects of circumcision on sexual function and sexual pleasure in a substudy of 2784 participants in the RCT of circumcision at Kisumu, Kenya. He found absolutely no difference between circumcised men and uncircumcised controls at 12 months after circumcision, in terms of ejaculation problems (too soon or too late), difficulty achieving erections, and pain or lack of pleasure during sex.

Interestingly the number of men reporting these problems declined rapidly from baseline to 12 months in both circumcised and uncircumcised men: for instance, 7-8% of men at baseline reported erectile dysfunction but only 1-2% at 12 months, regardless of circumcision status.

This unexplained finding may be due to men wishing to please investigators or with ‘regression to the mean’ (whereby minorities in surveys tend to join the majority as time goes on) but, commented Kreiger, ‘it shows the value of having a control group’ as without one it would have seemed that circumcision improved sexual function.

He also found, in a survey of sexual pleasure in circumcised men where a control group was not interviewed, that men reported that post-circumcision they were ‘more sensitive’ rather than less, achieved better orgasms and ‘found it easier to put on a condom ‘ but these results should be subject to the same caution.

I think I’ve been circumcised…

Bertan Auvert, who was principal investigator in the first RCT of circumcision at Orange Farm in South Africa, reported results that also showed how careful researchers have to be in accepting findings at face value. His survey reached 1680 households in Orange Farm and asked them about circumcision status and willingness to be circumcised or for their partner to be circumcised, and also tested participants for HIV. The researchers interviewed 1201 men and 1399 women. Nearly 50% of the respondents were Zulu, who are not traditionally circumcised. HIV prevalence was high, 12% in men (peaking at 41% at the age of 40) and 27% in women (peaking at 44% at the age of 30).

Almost 28% of male respondents said they were ‘circumcised’. But on further investigation – which meant showing interviewees photographs of circumcised and uncircumcised penises – 45% of men who said they were circumcised in fact were not and had intact foreskins. It turned out that there was confusion between the terms for ‘initiation ceremony’ and ‘circumcision’. One astounded youth said, when shown a photo, “I went to an initiation school. I thought I was circumcised. I am really surprised!” Others had told relatives they were circumcised but had in fact ducked out of the operation.

Of the men who actually had been circumcised, 84% reported that it ‘made sex better’ - but then so did 75% of the men who it transpired had not actually been circumcised, casting doubt on the value of this answer.

HIV prevalence was tied to true, rather than perceived, circumcision status; 20% of uncircumcised men had HIV, as did 18% of men who said they were circumcised but in fact were not, compared with 6% of men who actually were circumcised.

Circumcision was then offered to all the uncircumcised men in the survey. Of the men in the survey who were uncircumcised, and knew it, 67.5% said they ‘definitely’ would get circumcised, and 14% said ‘maybe’. Of these, 72% eventually did get circumcised, meaning that 59% of the uncircumcised men in the survey eventually were circumcised. However being offered circumcision was dependent on men self-defining as being uncircumcised, and the men who thought they were circumcised - but in fact were not - were not offered circumcision during the survey period because the confusion over terms was clarified too late.

Bertran warned investigators to make sure that people truly understand what they are being asked and are not just trying to please investigators, and that in the case of circumcision, investigators should take photos with them to show what it meant.


White R et al. Male circumcision for HIV prevention in sub-Saharan Africa: who, what and when? XVII World AIDS Conference, Mexico City. Abstract TUAC0302. 2008.

Lohse N et al. Challenges in developing models to estimate the impact of male circumcision on the HIV epidemic. XVII World AIDS Conference, Mexico City. Abstract TUAC0303. 2008.

Sawe F et al. Using male "traditional circumcision" as novel approaches for HIV prevention messages: experiences & opportunities from the Southern Rift Valley of Kenya. XVII World AIDS Conference, Mexico City. Abstract TUAC0304. 2008.

Krieger JN et al. Adult male circumcision: effects on sexual function and sexual satisfaction. XVII World AIDS Conference, Mexico City. Abstract TUAC0305. 2008.

Taljaard D et al (presenter Auvert B). Estimating the uptake of safe and free male circumcision in a South African community. XVII World AIDS Conference, Mexico City. Abstract TUAC0306. 2008.