On Friday, the W.H.O.’s Strategic Advisory Group of Experts and Malaria Policy Advisory Committee recommended that several pilot projects be carried out in Africa to make sure the vaccine is not even less effective in real-world settings than it has been in carefully monitored clinical trials.

It is not yet clear whether anyone will pay for the projects, which could take another five years. The vaccine has been developed by the pharmaceutical giant GlaxoSmithKline, but with donor support for testing. Two obvious sources of funds — the GAVI, the Vaccine Alliance, and the Global Fund to Fight AIDS, Tuberculosis and Malaria — said in a joint statement on Friday that their boards were still undecided.

“We need additional information,” Dr. Vasee Moorthy, leader of the W.H.O.’s vaccine development team, said of the committees’ desire for testing in several hundred thousand more children before vaccinating millions.

The vaccine requires three doses when a child is 5 months to 9 months old and a fourth at about age 2. In poor countries, children get most of their shots between their second and fourth months of life, and it is not clear that parents or African health care systems will be able to follow more complex schedules.

Children who miss even one dose are left unprotected, said Dr. Andrea Bosman, the W.H.O.’s chief of malaria prevention. Protection is known to last only four years, and it is unclear whether more boosters would be needed.