Trials of around 8,000 men took place in Uganda and Kenya. The trial in Kenya found a 53% reduction in new HIV infections in heterosexual men who were circumcised while the Ugandan study reported a drop of 48%.
Results last year from a study in 3,280 heterosexual men in South Africa, which was also stopped early, showed a 60% drop in the incidence of new infections in men who had been circumcised.
There are several reasons why circumcision may protect against HIV infection.
Specific cells in the foreskin may be potential targets for HIV infection and also the skin under the foreskin becomes less sensitive and is less likely to bleed reducing risk of infection following circumcision.
When Aids first began to emerge in Africa, researchers noted that men who were circumcised seemed to be less at risk of infection but it was unclear whether this was due to differences in sexual behaviour.
A modelling study done by international Aids experts earlier this year showed that male circumcision could avert about six million HIV infections and three million deaths in sub-Saharan Africa.
A further trial in Uganda to assess the risk of HIV transmission to female partners is due to report in 2008 but the effect among men who have sex with men has not yet been studied.
Dr Kevin De Cock, director of the HIV/Aids department of the World Health Organization told the BBC the results were a "significant scientific advance" but were not a magic bullet and would never replace existing prevention strategies.
"We will have to convene a meeting which we hope will happen quite soon to review the data in more detail and have discussions about the implications.
"This is an intervention that must be embedded with all the other interventions and precautions we have. Men must not consider themselves protected. It's a very important intervention to add to our prevention armamentarium."
Dr De Cock said that countries in Africa who wanted to use this approach would still have to decide what age groups to target and there would have to be training and hygienic practices in place.
"This is about as good epidemiological data as we can request. There will be many other research questions about implementation but this is very persuasive."
NIH director Dr Elias Zerhouni said: "Male circumcision performed safely in a medical environment complements other HIV prevention strategies and could lessen the burden of HIV/Aids, especially in countries in sub-Saharan Africa where, according to the 2006 estimates from UNAids, 2.8 million new infections occurred in a single year."
But Tom Elkins, Senior Policy Officer at the National AIDS Trust warned: "There is a real danger in sending out a message that circumcision can protect against HIV. This is not the case and could lead to an increase in unprotected sex.
La Organización Mundial de la Salud (OMS) ha publicado una serie de estudios que indican que una forma efectiva de para prevenir enfermedades de transmisión sexual, entre ellas el Sida, sería a través de las circuncisiones sistemáticas masculinas.
Incluso hace unos años la Agencia Nacional de Investigación Francesa sobre Sida (Inserm) realizó un estudio que también confirmaba esta hipótesis. De acuerdo a esta hipótesis la circuncisión ayudaría a reducir el nivel de riesgo de contraer VIH debido a que el prepucio está cubierto de células que el virus aparentemente infecta con facilidad.
A pesar de estas investigaciones, no son pocos que han alzado la voz para mostrarse contrarios a esta teoría. Incluso funcionarios de salud de la Organización de de Naciones Unidas (ONU) aseguraron en su tiempo que era necesario realizar más estudios para llegar a confirmar tal teoría.
Lo cierto es que por el momento no hay nada confirmado, por lo que el uso de preservativos durante toda una relación sexual sigue siendo hasta ahora el único método eficaz para evitar el contagio de enfermedades de transmisión sexual.
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