New malaria vaccine first to reach WHO efficacy demand

Malaria kills hundreds of thousands of children each year. Now, an early stage malaria vaccine trial in Africa has shown encouraging results.

A malaria vaccine trial in Burkina Faso has shown promising results for the fight against the disease, which killed more than 400,000 people in 2019.

The results of the trial, published on Preprints with The Lancet and currently awaiting peer review, showed that the R21/Matrix-M vaccine had 77% efficacy over 12 months of follow-up.

It is the first vaccine to meet the World Health Organization's (WHO) Malaria Vaccine Technology Roadmap goal of a vaccine with at least 75% efficacy.

The trial involved 450 children, aged 5-17 months. Participants were split into three groups — the first two groups received the R21/Matrix-M, with either a low dose or high dose of Matrix-M, and the control group got a rabies vaccine.

Vaccine efficacy in the group with a lower dose of Matrix-M was 71% and no serious side effects were noted.

The researchers have now started recruitment for a bigger trial to assess large-scale safety and efficacy in 4,800 children, aged 5-36 months, across four African countries.

The trial is "highly encouraging," said Julian Rayner, a malaria researcher and the director of the Cambridge Institute for Medical Research at the University of Cambridge in the UK, who was not involved in the study.

"It's an early-stage trial, the data from that trial is very encouraging but it's a [small] number of children and so it provides clear justification to go on

to bigger trials in other locations," Rayner told DW.

Children most affected

Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. There are five parasite species that cause malaria in humans, and two of these species — P. falciparum and P. vivax — pose the biggest threat.

It causes a wide range of symptoms including fever, headache, malaise, gastrointestinal issues, back pain, coughing, and neurologic complaints like dizziness, confusion and coma.

There were an estimated 229 million cases of malaria worldwide in 2019, according to the WHO, and a disproportionately large share of the malaria burden falls on Africa, where 94% of malaria cases and deaths occurred in 2019. Children under the age of five account for 67% of all malaria deaths worldwide.

People who live where there is a lot of malaria and get infected repeatedly as they grow up can naturally develop some level of immunity.

"It's not fully protective immunity, it's not that you never catch malaria again, but you don't get as severe symptoms and severe outcomes," Rayner told DW. "That's why the majority of severe cases are in young children because those who have survived long enough and are older have developed that natural immunity."

Until now, only one other vaccine, called RTS,S, has been shown to significantly reduce malaria and life- threatening severe malaria in young African children.

Among children aged 5–17 months who received 4 doses of RTS,S, the vaccine prevented approximately 39% of malaria cases over four years of followup and about 29% of severe malaria cases, according to the WHO.

Drug resistance a problem

When treated with medication early enough, someone with malaria can recover, but if it gets too severe it may be too late for the drugs to work; there is also a big problem with drug resistance.

"The parasites have developed resistance to a number of the frontline drugs," said Rayner. "That's why an effective vaccine is so important — because we need a new approach."

Malaria parasites have also developed sophisticated mechanisms to evade the immune response, Rayner told DW.

"There is no vaccine in wide use, so any positive result is incredibly exciting because malaria is a devastating disease and a massive public health challenge," said Rayner.