In the Bangkok perinatal HIV study oral zidovudine given during late pregnancy and labour to non-breast feeding women reduced the rate of mother to child transmission of HIV by 51% (95% confidence interval 15 to 71%).1 The investigators concluded that this intervention may help prevent HIV infection in children in developing countries, and the policy director for the treatment action group said, “If we can get this incredible health benefit for 80 bucks a pop, then we can really make a difference around the world.”2 Are these conclusions and expectations justified?

After the landmark ACTG076 trial, which showed that a complex and expensive antiretroviral regimen reduced mother to child transmission by 67%,3 the Thai results are clearly an important step forward. The short Thai regimen is cheaper and less complex, and hence likely to be attractive to countries unable to afford the 076 regimen. Paradoxically,the reaction to the results of this trial may pose a threat to the health of Africa's poorest women and their children. Within days of the release of the Thai data investigators studying other regimens closed recruitment to the placebo arms of their trials, and at a recent …