The R21/Matrix-M vaccine was designed in 2011 as a potential improvement on the RTS,S/AS01 malaria vaccine designed in the 1980s. A phase II trial in Burkina Faso, reporting in 2021, was the first to show that R21/Matrix-M could reach the WHO-specified target of 75% efficacy in African children. The most recent phase III results were published in The Lancet last week.
The trial investigators immunised over 4,800 young children in a trial in Burkina Faso, Kenya, Mali and Tanzania and found on average 78% vaccine efficacy over the first year of follow-up across all sites in the 5-17 month age group, the age range group which is studied for most malaria vaccines. Efficacy over this period was broadly similar across sites and in different transmission settings. Safety data from the trial have been reassuring with no serious adverse events linked to immunisation. No other vaccine has reported over 55% efficacy in the same age group. A booster dose after a year maintained good efficacy over the following 6-12 months. The vaccine also reduced infection rates in children measured at 12 and 18 months after vaccination suggesting a potentially beneficial effect in reducing malaria transmission.