Scientists hail landmark approval of malaria vaccine, but point to challenges ahead

More than 130 years after the appointment of the Plasmodium parasites behind malaria in 1890, the world now has its first vaccine approved against them. While many malaria researchers have celebrated the development, others have expressed concerns about the deployment of a moderately effective vaccine.

On October 6, the World Health Organization (WHO) gave the green light to the vaccine – called RTS, S – and recommended its widespread use in children under 5 in Africa, home to the malaria parasite. the most deadly, Plasmodium falciparum.

“The RTS, S malaria vaccine – over 30 years of manufacture – is changing the course of public health history,” WHO Director-General Tedros Adhanom Ghebreyesus said at a briefing. press announcing approval.

Compared to other childhood vaccinations, it has a modest efficiency, preventing about 30% of severe malaria after a series of four injections.

Nonetheless, a modeling study suggests that it could prevent 23,000 child deaths per year, if the full dose series were rolled out to all children in countries with high malaria incidence – a significant breach in the heavy toll of malaria. disease, which cost 411,000 people. lives in 2018.

Leaders across Africa are now considering whether and how to deploy it. In Mali, for example, Alassane Dicko, a malaria researcher at the University of Bamako said Nature that shortly after the WHO announcement, the country’s health minister asked him what Mali needed to do to get the vaccine.

“I told him that we had to lobby as a country, at the highest levels of our government, to make this vaccine available at an affordable cost as soon as possible,” he adds.

Three-decade effort

Researchers have developed and tested the RTS, S vaccine – also known by its brand name, Mosquirix – since 1987, at a cost of over US $ 750 million. This was primarily funded by the Bill & Melinda Gates Foundation in Seattle, Washington and the London-based pharmaceutical company GlaxoSmithKline (GSK).

Although clinical trials were completed in 2015, WHO subsequently recommended pilot studies to determine the feasibility and safety of this multidose vaccine outside of a clinical trial.

Gavi, the Vaccine Alliance, a health partnership based in Geneva, Switzerland, has helped fund pilot programs that have distributed 2.3 million doses of vaccine to Ghana, Kenya and Malawi. He reports that in these studies, hospitalizations for severe malaria decreased by about 30%. These results have given WHO the confidence to recommend four doses of the vaccine for children living in areas with moderate to high malaria transmission.

However, Dicko says countries could achieve even greater declines in hospitalizations and deaths through tailor-made deployments.

In August, he and his colleagues published the results of a clinical trial finding that the RTS, S vaccine reduced childhood malaria deaths by 73% when children received three doses before the rainy season – when malaria peaked – and a fourth and fifth dose before the rainy season in subsequent years. Notably, this was done in conjunction with a method called seasonal malaria chemoprevention, in which healthy children take monthly antimalarial drugs to prevent illness.

In addition to how the vaccine is deployed, another question countries will need to answer is how much it will cost to buy and distribute it – and whether donors will help foot the bill.

The vaccine manufacturer GSK issued a statement committing to make available 15 million annual doses just above the cost of production. However, around 100 million doses will be needed each year if all children in high burden countries are to receive the injections.

eclipse existing measures?

Some researchers worry that the enthusiasm for a vaccine overshadows existing malaria control measures that are already often underfunded, including insecticide programs and functioning health systems.

At a potential cost of around $ 5 per dose, the researchers suggest the deployment of the vaccine, including its distribution, would cost around $ 325 million to administer each year in ten African countries with high malaria incidence. They point out that in some of these countries, other malaria control measures have failed due to lack of support.

“I respect the researchers involved in this massive effort, but the reality is that so much money has been invested in this vaccine, even when the results of the studies are disappointing,” says Badara Cissé, malaria researcher at the Institut de Health Research, Epidemiological Surveillance and Training, in Dakar, Senegal, who adds, “I don’t think a vaccine that is 30% effective would be acceptable to Americans.

Despite this, he and James Tibenderana, a Ugandan epidemiologist at the Malaria Consortium in London, say the RTS, S vaccine could have an impact in some areas. To achieve this, Tibenderana stresses the need for extensive communication campaigns, so that disinformation does not hinder deployment.

“People will wonder why a 30-year-old, partially effective vaccine is suddenly introduced during a pandemic – and only targets Africans,” he says. “The misinformation around COVID-19 vaccines should teach us that we cannot take community trust for granted. “

Despite a long way to go, he and others are grateful for the WHO decision. “With the devastation of COVID-19, and with stalled progress on the fight against malaria, and the news of resistance to antimalarial drugs, it’s uplifting to see positive news, ”he says.

This article is reproduced with permission and was first publication October 8, 2021.