The World Health Organization has recommended a new vaccine, R21/Matrix-M, the world’s second vaccine to prevent malaria in children.

This comes after Phase III trials which enrolled 4,800 children — aged five months to three years — in four countries: Mali, Burkina Faso, Tanzania, and Kilifi in Kenya. In Kenya, where 600 children were recruited, the trials were led by Prof Mainga Hamulaba, the head of clinical research and clinical trials at the Kemri-Wellcome Trust Research Programme.

In areas with highly seasonal malaria transmission (where malaria transmission is largely limited to four or five months per year), the R21 vaccine was shown to reduce symptomatic cases of malaria by 75 percent during the 12 months following a three-dose series.

“A fourth dose given a year after the third maintained efficacy. This high efficacy is similar to the efficacy demonstrated when RTS,S (the world’s first malaria vaccine) is given seasonally.

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The vaccine showed good efficacy (66 percent) during the 12 months following the first 3 doses,” WHO noted.

Because availability of RTS,S is limited, addition of R21 to the list of WHO-recommended malaria vaccines is expected to result in sufficient vaccine supply to children in areas where malaria is a public health risk.

In its 2022 report, WHO noted that though there has been a decline of deaths due to malaria to just over 600,000 in 2020, Africa still accounts for more than 95 percent of the global burden and 96 percent of malaria deaths.

“To build on the long-standing work on malaria, the team in Kilifi led by Prof Hamaluba has been on course to carry out trials for the R21 Vaccine, including conducting the Phase 1 trial which first looked at the safety of the R21 vaccine in Africa,” Kemri-Wellcome Trust said.

In the Phase III trial, the 600 children recruited for the trial in Kilifi were randomised to one of two groups: one group receiving the R21 vaccine and the other a licensed rabies vaccine.

The screened eligible children were given the first three doses of the vaccine at 28-day intervals (primary series) while the fourth dose (booster) was given 12 months after the third dose.

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“The antibody and efficacy responses a month after the initial vaccination was higher in the younger vaccines (5-17 months compared to 18-36 months). The vaccine targets the CSP antigen like the RTS’S vaccine but can be used at a much lower dose than the RTS’S vaccine, uses a simpler saponin adjuvant and can be manufactured at very large-scale and at a lower cost per dose thus making it highly cost effective,” the researchers explained.

The next steps for the R21 malaria vaccine will now include completing the ongoing WHO prequalification which would enable international procurement of the vaccine for broader rollout, WHO added.

Dr Tedros Adhanom Ghebreyesus, director-general of the WHO, said it was a moment of “great pleasure”.

“I used to dream of the day we would have a safe and effective vaccine against malaria, now we have two,” he said.

Additional reporting by BBC.