IN July, the world’s first malaria vaccine got the endorsement of European regulators, in what was seen as a critical step in fighting a disease that kills half a million in Africa every year.
Now, the RTS,S vaccine – sold under the brand name Mosquirix – has received ‘cautious’ backing from an advisory group to the World Health Organisation (WHO), who say it should be rolled our in limited pilot demonstrations in the continent.
The lukewarm endorsement comes because studies have shown the vaccine is only partially effective against malaria, requiring four doses spread over 18 months, and even then only offers modest protection.
“If we can’t get four doses of this vaccine into children, we’re not going to be using it,” Jon Abramson, a paediatric infectious disease specialist at Wake Forest School of Medicine in Winston-Salem, North Carolina, and chair of the WHO Strategic Advisory Group of Experts (SAGE) on Immunization, said in a press briefing last week.
The vaccine has been under development for 28 years by London-based drug firm GlaxoSmithKline (GSK), which, together with funders such as the Bill and Melinda Gates Foundation have spent $565 million on the drug, according to a report in the latest edition of science journal Nature.
WHO’s director general is expected to formally endorse the vaccine pilots this month, but the imperfections of the vaccine have been documented – in trials with more than 15,000 children, who were followed for up to four years in seven countries in sub-Saharan Africa, found that a series of four shots reduced the number of malaria cases by only 36% in young children, and by 26% in infants.
Still, even this would be sufficient to save hundreds of thousands of lives in the region, as most of those who die from malaria are children under the age of five.
The field trials will involve up to 1 million children, living in areas with medium to high incidence of malaria, to determine whether parents bring their children back for all four doses of the vaccine: without the final dose, RTS,S provides no more protection against malaria than do other controls like insecticide-treated bed nets, Abramson said.
The pilots will also investigate safety issues associated with the vaccine, such as the potential to develop meningitis.
All this is needed to ensure that precious funding is not wasted, he said. “If this vaccine is not effective and we use it widely, we have spent a ton of money where it could be better placed.”
A study published in Nature on 21 October revealed that the vaccine’s poor performance in clinical trials in partly because it mimics the surface proteins of a strain of the malaria parasite Plasmodium falciparum not commonly found in Africa.
When researchers first made RTS,S-like vaccines nearly three decades ago, they did not have the tools to measure the extent of this variation, or its consequences for their vaccine.
If it had been a perfect match, the efficacy of the vaccine over a year could have been at least 50% higher. Re-designing the vaccine so that it is more effective in the African context ‘could take years’, researchers say.
“It’s not trivial to tweak the vaccine to match the prevalent strains in an area,” David Kaslow, who oversees the vaccine’s development at the non-profit health organization PATH. told Nature, “but it’s not impossible.”