The European Medicines Agency (EMA) has recommended approving what would be the world's first licensed malaria vaccine, even though it's only about 30 percent effective and its protection fades over time.
In a statement Friday, the agency endorsed the vaccine's use outside Europe, a regulatory process that helps speed new medicines to the market.
The recommendation to license the vaccine, known as Mosquirix and made by GlaxoSmithKline, must still be approved by the European Commission.
The World Health Organization will next consider the evidence and recommend how the shot be used. It's unlikely donors would pay for the vaccine without WHO's guidance, especially since it only protects about one-third of the children vaccinated.
"This is not the big game-changer that we were hoping for," said Dr. Martin De Smet, a malaria expert at Doctors Without Borders. "The vaccine itself remains disappointing, but this is an important step forward."
Still, De Smet said the vaccine could help reduce the burden of malaria, which is one of the biggest killers of children in the world, claiming the life of one child every minute. It infects about 200 million people per year and killed an estimated 584,000 people in 2013, the vast majority of them babies in sub-Saharan Africa.
"In countries where children get four to six episodes of malaria a year, this will make a big difference," he said, adding that people should still keep using bed nets to protect against mosquitoes.
Andrew Witty, GSK's chief executive, said the EMA's positive opinion was an important step toward making the world's first malaria vaccine available.
"While RTS,S on its own is not the complete answer to malaria, its use alongside those interventions ... such as bed nets and insecticides would provide a very meaningful contribution to controlling the impact of malaria on children in those African communities that need it the most," he said.
Mosquirix was assessed for quality, safety and efficacy under a special procedure that allows the EMA to evaluate a product even if it will not be marketed in the European Union.
Beyond the WHO's November recommendation, Mosquirix would still have to be reviewed by national regulatory authorities in any country wishing to use it. The WHO said this meant it is unlikely to be rolled out anywhere until at least 2017.
Global health experts have long hoped scientists would be able to develop an effective malaria vaccine, and researchers at GSK have been working on RTS,S for 30 years. The shot also contains an adjuvant, or booster, made by U.S. biotech company Agenus.
Expectations that Mosquirix could be a final answer to wiping out malaria were dampened when trial data released in 2011 and 2012 showed it reduced episodes of malaria in babies aged 6-12 weeks by only 27 percent, and by around 46 percent in children aged 5-17 months.
The EMA recommendation is that the shot should nevertheless be used in babies in the full age range covered in the trials, from six weeks to 17 months.
Some malaria specialists have expressed concern that the complexities and costs of deploying this first vaccine when it provides only partial protection make it less attractive and more risky.
"The timing, duration and outcomes of some of the critical steps to possible vaccine implementation in African countries are not yet known," said David Kaslow, vice president of product development at PATH, a Seattle-based nonprofit that promotes innovations in international health and which also helped support the development Mosquirix.
However, Joe Cohen, a GSK scientist who has led the development of Mosquirix since 1987, said on he had no doubt the vaccine could significantly reduce the toll of sickness and death caused by the malaria among African children.
"I have absolutely no reservations in terms of rolling this vaccine out," he told Reuters. "Why? Because the efficacy, when translated into cases averted and deaths averted, is just tremendous. It will have an enormously significant public health impact."
GSK has promised it will make no profit from Mosquirix, pricing it at the cost of manufacture plus a 5 percent margin, which it will reinvest in research on malaria and other neglected tropical diseases.
Sources involved in planning for Mosquirix's potential future use have told Reuters they've been advised to work with a price tag of around $5 per dose, which would bring the cost of a recommended four-dose immunization to $20.