Background
Male circumcision(MC) can reduce HIV acquisition. However, a better understanding of the indirect protective effect of MC on sexually transmitted infections (STIs) is required.
Objective
To assess the incremental benefits conferred by MC on HIV infection at the individual-level in circumcision trials (no herd immunity effect) and at the population-level (with herd immunity effect) due to its protective effect against other STIs.
Methods
A dynamical stochastic model of HIV and STI infections in a Kenyan population was used to simulate the impact of circumcision offered to a minority of trials participants or to a large fraction of men in order to study the protective role of MC on HIV infection at the individual-level and at the population-level, respectively.
Results
Less than 20% of the HIV infections prevented in the circumcised arm of the circumcision trials (individual-level) could be attributable to MC efficacy against STIs rather than MC efficacy against HIV. At the population-level, MC can significantly reduce HIV prevalence especially among males and among females in the longer term. However, even at the population-level, the long-term incremental impact of MC on HIV due to the protection against STI is modest (even if MC efficacy against the STI and STI prevalence was high).
Discussion
The protection of MC against STI contributes little to the overall effect of MC on HIV in the trials. Additional work is needed to identify if the protective effect of MC efficacy against STIs can have a significant incremental benefit on the HIV epidemic.