World Health Organization endorses much anticipated second malaria vaccine

2 October 2023 — The World Health Organization (WHO) today recommended widespread use of a second vaccine against malaria, a disease that kills more than half a million children each year, most of them in sub-Saharan Africa. The new vaccine, called R21/Matrix-M, follows in the footsteps of the first malaria vaccine, called Mosquirix or RTS,S, for which WHO made a similar recommendation 2 years ago. That vaccine, however, is in short supply, with only about 18 million doses expected to be available through 2025. The addition of a second vaccine is “expected to close the gap between supply and demand, and has the potential to save tens of thousands of lives each year,” Hanna Nohynek, chair of WHO’s Strategic Advisory Group of Experts on Immunization (SAGE), said in a press conference today.

Both vaccines contain a protein from the surface of the parasite that causes the deadliest form of malaria, Plasmodium falciparum. At a meeting last week, SAGE considered the latest encouraging data from a phase 3 trial of R21 involving 4800 children, which were made public last week as a preprint hosted by The Lancet. Although no clinical trial has directly compared the protection offered by the two vaccines, “we have every indication that they will be very similar,” Dyann Wirth, chair of WHO’s Malaria Policy Advisory Group, told the press conference. Both vaccines show roughly 75% efficacy against clinical malaria when they are given, in combination with antimalarial drugs, to children just before the rainy season in areas where the weather change greatly increases malaria transmission.

R21, which was developed at the University of Oxford, still needs to complete WHO’s so-called prequalification process, which looks not only at safety and efficacy, but also manufacturing practices and quality control. That process is underway and should be complete in “the near future,” Kate O’Brien, director of WHO’s Department of Immunization, Vaccines and Biologicals, said at the press conference. Once the vaccine receives prequalification, it will be eligible for purchase by groups such as UNICEF and Gavi, the Vaccine Alliance, which buy vaccines for distribution in many low-income countries. WHO’s experts predicted today that R21 could be widely available for use in the second half of 2024.

At least 28 countries have drawn up plans to introduce vaccines as part of their malaria control programs, WHO said today. Both vaccines require three initial doses within several months, plus a fourth dose 12 months later, and will likely require additional boosters to maintain high levels of protection. Whether countries choose R21 or Mosquirix could depend on several things, O’Brien told the press conference. The estimated price per dose of between $2 and $4 for R21 means it may cost less than half as much as RTS,S, at least at first. The price difference won’t affect countries that receive vaccines from Gavi or UNICEF, O’Brien says, but could be relevant for some middle-income countries that purchase some of their own vaccines.

At the same time, O’Brien noted, some countries may opt for RTS,S because much more is known about its safety and efficacy; it has already been given to 1.8 million of children as part of clinical trials and its initial rollout, whereas data on R21 are only from a few thousand recipients.

The agency’s experts emphasized that the vaccine should be used in combination with already established malaria tools, including insecticide-treated bed nets, rapid diagnosis and treatment, and the use of antimalarial drugs to prevent infections. “It will be really important not to substitute the one intervention for the other,” said Mary Hamel, a WHO senior technical officer who has helped guide introduction of RTS,S in Malawi, Kenya, and Ghana. “We don’t want to roll out the vaccine and pull back on bed nets, which are also lifesaving. Adding these interventions on top of each other is where we’re really going to get high impact.”

The Serum Institute of India, one of the world’s largest vaccinemakers, is cooperating with Oxford to develop the vaccine and has said it will be able to produce 100 million doses per year starting as soon as next year. That should mean that by next year there will be enough doses for all countries that want to use the vaccines, says WHO Director-General Tedros Adhanom Ghebreyesus. “As a malariologist, today is a happy day,” he told the press conference. “I hope this will change the game.”

By Gretchen Vogel

SEE ALSO:

• Health Policy Watch: Second malaria vaccine gets WHO approval – 100 million doses ready for rollout