Washington — 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. Results were published Friday in the New England Journal of Medicine, a U.S. publication.
While still significant, the results were disappointing in having followed surprisingly positive findings last year, when a similar study suggested that RTS,S was almost twice as effective (47-56 percent) on slightly older children, those five to 17 months old.
If this most recent phase could replicate that level of efficacy among infants, researchers had hoped that RTS,S doses could become incorporated into the standard round of initial vaccinations commonly given to newborns - an approach that has now been proven safe.
"It's a little frustrating that we're seeing different levels of protection in different age groups compared to last year and this year," Andrew Witty, the CEO of GlaxoSmithKline, a major drugs manufacturer and one of the central partners in developing RTS,S, told journalists Friday from London.
"As it turns out, this phase of study was not the final step that I think many people might have hoped. But it's an important step and takes us further forward towards the goal we've been working toward over the past 50 years ... this remains the lead and most encouraging candidate vaccine."
Indeed, the new research constitutes the first time that scientists have found such high efficacy for an anti-malarial vaccine for infants. Witty notes that if the two rounds of study had been reversed, the psychological impact would be far different and the findings would undoubtedly have been widely lauded.
Further, the higher efficacy among the slightly older cohort remains extremely important, given that scientists have found that this age category has greater susceptibility to severe cases of malaria than do infants. While the ease of a single early vaccination would have been the most efficient scenario, researchers say they will now be looking into additional strengthening options, such as giving toddlers a booster later on.