In Ghana, Kenya and Malawi, more than 650,000 children have been vaccinated with RTS,S since 2019.
The vaccine reduced the number of infections by 39 per cent, according to preliminary results from an earlier study.
Children have to receive four doses.
Malaria, a life-threatening infectious disease transmitted by infected Anopheles mosquitoes, kills more than 400,000 people per year, according to the WHO. Two-thirds of them are children under the age of five.
“So far, accrued safety data from the evaluation of the pilot introduction is very reassuring,” a WHO spokesman said.
The WHO plans to decide before the end of the year whether to recommend its use in other countries.
On Wednesday, WHO is to present a new initiative to fight malaria, ahead of World Malaria Day on April 25.
RTS,S, is effective against Plasmodium falciparum, the malaria parasite most prevalent in Africa, but not Plasmodium vivax, which is prevalent outside Africa. Its active ingredient is made by British pharmaceutical company GSK.