Malaria booster vaccine: update

Malaria is a leading cause of morbidity and mortality worldwide. Researchers from the University of Oxford and their partners have today reported new findings from their Phase 2b trial following the administration of a booster dose of the candidate malaria vaccine, R21/Matrix-M™ – which previously demonstrated high-level efficacy of 77% over the following 12 months in young west African children in 2021.

In their findings (reported in The Lancet Infectious Diseases), they found that a vaccine booster dose at one year following a primary three-dose regime maintained high efficacy against malaria, and continued to meet the World Health Organization’s Malaria Vaccine Technology Roadmap goal of a vaccine with at least 75% efficacy. 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.

The co-inventor of a vaccine that could eradicate malaria has said he hopes it could be approved by as early as next year after the latest trial results were successful. Professor Adrian Hill, co-creator of the AstraZeneca Covid vaccine, said it was “the best [malaria] vaccine yet”. He has previously said he believes R21 could help to reduce deaths from the disease by 70% by 2030 and eradicate it by 2040.

This double-blind phase 1/2b randomised controlled trial was done in children aged 5–17 months in Nanoro, Burkina Faso. Eligible children were enrolled and randomly assigned (1:1:1) to receive three vaccinations of either 5 μg R21/25 μg Matrix-M, 5 μg R21/50 μg Matrix-M, or a control vaccine (the Rabivax-S rabies vaccine) before the malaria season, with a booster dose 12 months later. Children were eligible for inclusion if written informed consent could be provided by a parent or guardian. Exclusion criteria included any existing clinically significant comorbidity or receipt of other investigational products. A random allocation list was generated by an independent statistician by use of block randomisation with variable block sizes.

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.


Efficacy and immunogenicity of R21/Matrix-M vaccine against clinical malaria after 2 years’ follow-up in children in Burkina Faso: a phase 1/2b randomised controlled trial

Oxford university news bulletin

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