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The world’s first mass vaccination program against malaria, announced this week, is set to prevent millions of children from catching malaria and thousands dying from this debilitating disease.

The World Health Organization (WHO) has recommended widespread use of the RTS,S/AS01 (Mosquirix) vaccine in young children who are most at risk of malaria in Africa.

Malaria is a big deal

Mosquitoes spread the parasite Plasmodium falciparum from person to person when they bite. So until now, our fight against malaria has involved using mosquito nets to avoid being bitten and spraying insecticide to kill mosquitoes. Then there are drugs to prevent or treat malaria infection.

However, the parasite has developed resistance to antimalarial drugs and mosquitoes have developed resistance to insecticides. Nevertheless existing control measures have resulted in a significant decrease in the number of malaria deaths since 2000.

In recent years, however, progress has stalled. In 2019, malaria infection resulted in 409,000 deaths around the world, mostly in children under five years old, and 229 million new malaria cases.

So we need extra tools, such as an effective malaria vaccine, if we are to control the disease globally.

WHO’s recommendation to roll out the Mosquirix vaccine to children at high risk of infection with P. falciparum, which is widespread in Africa, is an important step towards controlling the deadliest of human malaria parasites.

What did the WHO recommend?

The WHO recommended four doses of the vaccine in children from five months old.

This recommendation follows recent results from a pilot program in Ghana, Kenya and Malawi, involving vaccinating more than 800,000 children since 2019.

The program showed delivering the vaccine is feasible and cost-effective in high-risk areas. It also increased the number of children (to more than 90%) who have access to at least one intervention to prevent malaria.

The vaccine has a good safety profile and reduces cases of clinical and severe malaria, which can be deadly.

What do we know about the vaccine?

Mosquirix is a “subunit” vaccine. This means it only contains a small part of the malaria parasite, which is produced as a synthetic protein.

This protein is coupled with an “adjuvant”, a molecule designed to stimulate a strong immune response.

The vaccine works mainly by stimulating the body to make antibodies against the parasite, neutralising it, and preventing it from entering liver cells. These are the first cells the parasite invades when it enters the body.

The vaccine also works by helping to mount an inflammatory response, when a different part of the immune system responds.