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Understanding the impact of male circumcision interventions on the spread of HIV in southern Africa.

Hallett TB, Singh K, Smith JA, White RG, Abu-Raddad LJ, Garnett GP - PLoS ONE (2008)

Bottom Line: Without additional interventions, HIV incidence could eventually be reduced by 25-35%, depending on the level of coverage achieved and whether onward transmission from circumcised men is also reduced.In the long-term, this could lead to reduced AIDS deaths and less need for anti-retroviral therapy.Circumcision will not be the silver bullet to prevent HIV transmission, but interventions could help to substantially protect men and women from infection, especially in combination with other approaches.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom. timothy.hallett@imperial.ac.uk

ABSTRACT

Background: Three randomised controlled trials have clearly shown that circumcision of adult men reduces the chance that they acquire HIV infection. However, the potential impact of circumcision programmes--either alone or in combination with other established approaches--is not known and no further field trials are planned. We have used a mathematical model, parameterised using existing trial findings, to understand and predict the impact of circumcision programmes at the population level.

Findings: Our results indicate that circumcision will lead to reductions in incidence for women and uncircumcised men, as well as those circumcised, but that even the most effective intervention is unlikely to completely stem the spread of the virus. Without additional interventions, HIV incidence could eventually be reduced by 25-35%, depending on the level of coverage achieved and whether onward transmission from circumcised men is also reduced. However, circumcision interventions can act synergistically with other types of prevention programmes, and if efforts to change behaviour are increased in parallel with the scale-up of circumcision services, then dramatic reductions in HIV incidence could be achieved. In the long-term, this could lead to reduced AIDS deaths and less need for anti-retroviral therapy. Any increases in risk behaviours following circumcision, i.e. 'risk compensation', could offset some of the potential benefit of the intervention, especially for women, but only very large increases would lead to more infections overall.

Conclusions: Circumcision will not be the silver bullet to prevent HIV transmission, but interventions could help to substantially protect men and women from infection, especially in combination with other approaches.

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Related in: MedlinePlus

Projected impact of male circumcision interventions over time with different levels of coverage achieved if, (a) circumcised men are 60% less likely to get infected but there is no effect on male-to-female transmission; and, (b) circumcised men are 60% less likely to get infected and circumcised men are 30% less likely to transmit infection.In each panel, five epidemic projections show circumcision interventions with 30% (red line), 45% (yellow line), 60% (blue line), 75% (brown line) or 90% (green line) of men being circumcised. The output is the ratio of HIV incidence when the intervention is simulated relative to the projection with no intervention. Endemic HIV prevalence before the intervention is 23%.
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pone-0002212-g003: Projected impact of male circumcision interventions over time with different levels of coverage achieved if, (a) circumcised men are 60% less likely to get infected but there is no effect on male-to-female transmission; and, (b) circumcised men are 60% less likely to get infected and circumcised men are 30% less likely to transmit infection.In each panel, five epidemic projections show circumcision interventions with 30% (red line), 45% (yellow line), 60% (blue line), 75% (brown line) or 90% (green line) of men being circumcised. The output is the ratio of HIV incidence when the intervention is simulated relative to the projection with no intervention. Endemic HIV prevalence before the intervention is 23%.

Mentions: The overall impact of circumcision interventions achieving different levels of coverage is examined in Figure 3. The relationship between coverage and overall impact at the population level is strong and non-linear, meaning that marginal increases in coverage lead to greater marginal gains in preventing new infections. With no effect on male-to-female transmission assumed, and 50% of men circumcised, once a new endemic prevalence is reached after 15–20 years, incidence across men and women is reduced by ∼20% (Figure 3(a)). However, it will take time for that full effect to be realised. Although the direct effect of reduced incidence in the circumcised men will almost immediately follow healing, reductions in incidence among women and uncircumcised men rely on prevalence declining among circumcised men. Since median survival with HIV infection is approximately 10 years, these indirect effect of the interventions emerge gradually over decades. This means that cumulative measures of the impact of the epidemic, which include infections prior to when the full effect is exerted, provide a less substantial indication of the effectiveness of this intervention [50]. Furthermore, over the long-term, interpreting the reduction in the number of infections due to the intervention as ‘infections averted’ is not straight forward as faster population growth (by reducing the effects of AIDS-related mortality and sub-fertility) can contribute to greater numbers of infections despite the rate of incidence being reduced.


Understanding the impact of male circumcision interventions on the spread of HIV in southern Africa.

Hallett TB, Singh K, Smith JA, White RG, Abu-Raddad LJ, Garnett GP - PLoS ONE (2008)

Projected impact of male circumcision interventions over time with different levels of coverage achieved if, (a) circumcised men are 60% less likely to get infected but there is no effect on male-to-female transmission; and, (b) circumcised men are 60% less likely to get infected and circumcised men are 30% less likely to transmit infection.In each panel, five epidemic projections show circumcision interventions with 30% (red line), 45% (yellow line), 60% (blue line), 75% (brown line) or 90% (green line) of men being circumcised. The output is the ratio of HIV incidence when the intervention is simulated relative to the projection with no intervention. Endemic HIV prevalence before the intervention is 23%.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2387228&req=5

pone-0002212-g003: Projected impact of male circumcision interventions over time with different levels of coverage achieved if, (a) circumcised men are 60% less likely to get infected but there is no effect on male-to-female transmission; and, (b) circumcised men are 60% less likely to get infected and circumcised men are 30% less likely to transmit infection.In each panel, five epidemic projections show circumcision interventions with 30% (red line), 45% (yellow line), 60% (blue line), 75% (brown line) or 90% (green line) of men being circumcised. The output is the ratio of HIV incidence when the intervention is simulated relative to the projection with no intervention. Endemic HIV prevalence before the intervention is 23%.
Mentions: The overall impact of circumcision interventions achieving different levels of coverage is examined in Figure 3. The relationship between coverage and overall impact at the population level is strong and non-linear, meaning that marginal increases in coverage lead to greater marginal gains in preventing new infections. With no effect on male-to-female transmission assumed, and 50% of men circumcised, once a new endemic prevalence is reached after 15–20 years, incidence across men and women is reduced by ∼20% (Figure 3(a)). However, it will take time for that full effect to be realised. Although the direct effect of reduced incidence in the circumcised men will almost immediately follow healing, reductions in incidence among women and uncircumcised men rely on prevalence declining among circumcised men. Since median survival with HIV infection is approximately 10 years, these indirect effect of the interventions emerge gradually over decades. This means that cumulative measures of the impact of the epidemic, which include infections prior to when the full effect is exerted, provide a less substantial indication of the effectiveness of this intervention [50]. Furthermore, over the long-term, interpreting the reduction in the number of infections due to the intervention as ‘infections averted’ is not straight forward as faster population growth (by reducing the effects of AIDS-related mortality and sub-fertility) can contribute to greater numbers of infections despite the rate of incidence being reduced.

Bottom Line: Without additional interventions, HIV incidence could eventually be reduced by 25-35%, depending on the level of coverage achieved and whether onward transmission from circumcised men is also reduced.In the long-term, this could lead to reduced AIDS deaths and less need for anti-retroviral therapy.Circumcision will not be the silver bullet to prevent HIV transmission, but interventions could help to substantially protect men and women from infection, especially in combination with other approaches.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom. timothy.hallett@imperial.ac.uk

ABSTRACT

Background: Three randomised controlled trials have clearly shown that circumcision of adult men reduces the chance that they acquire HIV infection. However, the potential impact of circumcision programmes--either alone or in combination with other established approaches--is not known and no further field trials are planned. We have used a mathematical model, parameterised using existing trial findings, to understand and predict the impact of circumcision programmes at the population level.

Findings: Our results indicate that circumcision will lead to reductions in incidence for women and uncircumcised men, as well as those circumcised, but that even the most effective intervention is unlikely to completely stem the spread of the virus. Without additional interventions, HIV incidence could eventually be reduced by 25-35%, depending on the level of coverage achieved and whether onward transmission from circumcised men is also reduced. However, circumcision interventions can act synergistically with other types of prevention programmes, and if efforts to change behaviour are increased in parallel with the scale-up of circumcision services, then dramatic reductions in HIV incidence could be achieved. In the long-term, this could lead to reduced AIDS deaths and less need for anti-retroviral therapy. Any increases in risk behaviours following circumcision, i.e. 'risk compensation', could offset some of the potential benefit of the intervention, especially for women, but only very large increases would lead to more infections overall.

Conclusions: Circumcision will not be the silver bullet to prevent HIV transmission, but interventions could help to substantially protect men and women from infection, especially in combination with other approaches.

Show MeSH
Related in: MedlinePlus