A nurse fills a syringe with malaria vaccine for an infant at the Lumumba Sub-County hospital in Kisumu, Kenya, July 1, 2022.

A nurse prepares to administer a malaria vaccine in Kenya.Credit: Baz Ratner/Reuters

A promising malaria vaccine was up to 80% effective at preventing the disease in young children who received a booster shot one year after their initial dose, exceeding a World Health Organization (WHO) target of 75% efficacy.

The clinical-trial results, published in The Lancet Infectious Diseases on 7 September1, add to data released last year, and show that immune responses — which waned over the year following the initial dose of vaccine — can be boosted back to initial levels.

The findings offer hope that the vaccine, called R21, could be an effective weapon in the fight against malaria, which is one of the biggest killers of children globally.

But public-health officials will require results from a bigger trial — with more than ten times as many participants, spread across four African countries — before they can confirm R21’s safety and utility, and roll it out on a larger scale. “There is still more work to be done,” says Matshidiso Moeti, the WHO’s regional director for Africa, who is based in Brazzaville in the Republic of Congo. “But I think this is very positive news.”

Century-long search

Nearly a century of searching for effective malaria vaccines has yielded well over 100 candidates that have been tested in people, Adrian Hill, a vaccinologist at the University of Oxford, UK, told reporters during a press briefing.

So far, the only one shown to be successful is a vaccine called RTS,S, produced by London-based pharma giant GSK. After decades of development, RTS,S was approved by the WHO on 6 September for broad use in regions with significant malaria transmission. It has been administered to more than 800,000 children in Ghana, Kenya, and Malawi, and is about 70% effective at preventing malaria in children when combined with conventional antimalarial drugs.

The R21 vaccine has been tested in 450 children aged between 5 and 17 months in Burkina Faso, a country in which malaria infections are seasonal. This could affect its apparent efficacy: a vaccine administered shortly before a seasonal malaria peak might seem to be more effective than one given in a country with a more even disease spread throughout the year. This is because children in the latter country could face a higher risk of infection after their vaccine-induced immunity has started to wane.

Results awaited from a larger trial of 4,800 children in 4 African countries, including 2 in which malaria is a year-round threat, could address that concern and solidify R21’s unblemished safety record. Hill’s team is analysing the data from that trial and hopes to update the WHO on the results by the end of September.

Rapid deployment

The key to R21’s impact on malaria might lie not just in its effectiveness, but also in its availability, says Hill. He and his collaborators have forged an agreement with the Serum Institute of India, based in Pune, to produce 200 million doses of the vaccine per year once the WHO gives the green light. By comparison, United Nations children’s fund UNICEF announced in August that it had awarded GSK a contract to supply 18 million doses of RTS,S over three years.

“Supply here is a real strength,” said Hill, who also noted that he expects R21 to be sold at less than half the price of RTS,S. “We hope that this will be deployed and available and saving lives certainly by the end of next year.”