GSK factory in Shanghai, China. | Photo by EPA First malaria vaccine moves closer to approval Remaining doubts center on implementation, cost and efficacy.

European drug regulators just gave a major lift to the world’s first malaria vaccine.

The European Medicine Agency on Friday adopted a positive scientific opinion for the drug — potentially paving the way for it to be recommended for approval by the World Health Organization later this year.

The regulatory group’s opinion does not constitute a recommendation, because Mosquirix will not be marketed outside Africa or sold to travelers on the continent, but the WHO on Friday said it welcomed the EMA assessment and called it a “major milestone for malaria vaccine development.”

A WHO official further added that the EMA advice “is not a recommendation to use this vaccine. WHO will provide our recommendations on use by November 2015,” adding that they will base their determination on factors not addressed by regulators, including feasibility of implementation, cost and cost-effectiveness, and “the public health value of the vaccine in relation to other available malaria control measures and vaccines.”

The mosquito-borne disease infects around 200 million people a year, according to WHO figures. In 2013, malaria killed about 584,000 people, the vast majority of whom were children under the age of five.

If approved, Mosquirix — developed by U.K. drug-maker giant GlaxoSmithKline and powerfully backed by the Bill and Melinda Gates Foundation — would give hope for treatments of infants in sub-Saharan African countries, where the disease is endemic.

Yet, despite optimism for the shot which has been under development for three decades, the chief obstacle for the vaccine’s approval rests in uncertainties surrounding its implementation and cost.

Final clinical trial data, on which the EMA decision was informed, only showed “modest protection” in African children administered shots, with a 56 percent protection rate in children aged between 5 and 7 months, and 31 percent in children between 6-12 weeks.

Further, the efficacy of the vaccine declined 12 months after being taken, pointing to the costly need for increased doses or booster shots to follow vaccination.

Both the EMA and the WHO cautioned that maintaining other protective efforts to combat the global disease, like bed nets and rapid diagnoses, was crucial.

“While (the drug) on its own is not the complete answer to malaria, its use alongside those interventions … would provide a very meaningful contribution to controlling the impact of malaria on children in those African communities that need it the most,” said Andrew Witty, GSK’s chief executive.

The company has not yet named a price for Mosquirix, but promised that it would not make any profit from the shot.