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Researchers unveiling critical trial results of a potentially major anti-malaria vaccine are expressing disappointment that the drug’s efficacy levels have proved lower than they had anticipated. Following on decades of research, the third phase of testing on a vaccine known as RTS,S found that the drug reduced malaria rates among infants (age six to 12 weeks) by about a third, far lower than expected. The study, funded largely by the Bill & Melinda Gates Foundation, is part of the largest malaria trial ever conducted, taking place in seven African countries.