Disappointment has greeted the publication of fresh data on a malaria vaccine co-developed by GlaxoSmithKline which shows that it was only 30% effective at protecting African infants.

Results from a large-scale Phase III trial, published in the New England Journal of Medicine, show that when administered along with standard childhood vaccines, the efficacy of RTS,S in infants aged 6 to 12 weeks (at first vaccination) against clinical and severe malaria was 31% and 37%, respectively, over 12 months of follow-up after the third vaccine dose. The disappointment stems from the fact that the efficacy observed with RTS,S last year in children aged 5-17 months of age against clinical and severe malaria was 55% and 47%, respectively.

Eleven research centres in seven African countries are conducting the trial (which included 6,537 children), together with GSK and the PATH Malaria Vaccine Initiative (MVI). Funding is also provided by the Bill and Melinda Gates Foundation.

Salim Abdulla, a principal investigator for the trial from the Ifakara Health Institute, Tanzania, acknowledged that "the efficacy is lower than what we saw last year with the older 5-17 month age category, which surprised some of us scientists at the African trial sites". He added that "it makes us even more eager to gather and analyse more data from the trial to determine what factors might influence efficacy against malaria and to better understand the potential of RTS,S".

GSK chief executive Sir Andrew Witty remained optimistic, saying "we believe these results confirm that RTS,S can help provide African babies and young children". He added that "we remain convinced that RTS,S has a role to play in tackling malaria and we will continue to work with our partners and other stakeholders to better understand the data".

Bill Gates noted that the efficacy "came back lower than we had hoped, but developing a vaccine against a parasite is a very hard thing to do". He noted that the trial is continuing "and we look forward to getting more data to help determine whether and how to deploy this vaccine".

Mr Gates' foundation has put in $200 million to the project with its backing for the MVI, while GSK has invested more than $300 million to date. The drugs major expects to invest more than $200 million before the completion of the project.