GlaxoSmithKline’s first-of-a-kind malaria vaccine Mosquirix will undergo real-world pilot studies in three African countries selected by the World Health Organization.

Starting next year, the pilots will enroll babies aged 5 to 17 months to test the vaccine’s efficacy in the real-world setting, and to study whether delivering four doses is feasible in healthcare-strapped, but malaria-heavy, sub-Saharan areas.

Back in 2015—despite an EMA green light for the shot based on phase 3 data involving more than 15,000 children in African countries—the WHO decided to evaluate the vaccine’s real-world performance before recommending it for a full rollout.

"Information gathered in the pilot program will help us make decisions on the wider use of this vaccine," Matshidiso Moeti, WHO regional director for Africa, said in the release. "Combined with existing malaria interventions, such a vaccine would have the potential to save tens of thousands of lives in Africa."

The WHO’s decision came as data showed the vaccine's efficacy dwindled over time. At four years, the vaccine reduced the number of clinical malaria cases in children aged 5 to 17 months by a not-so-reassuring 36%, a significant decline in the level of protection compared with the 45% detected in the previous 18-month follow-up.

But a 36% efficacy, if it actually plays out in real life, is still a clear benefit in the fight against malaria, given that the WHO tallied an estimated 212 million malaria cases and 429,000 malaria deaths in 2015, with the vast majority of victims under 5 years old.

The WHO said it chose the three African countries because their malaria rates remain high despite broad use of insecticidal bed nets and well-functioning immunization programs. It is up to the countries to decide which districts should be included in the pilot program, and malaria-heavy areas will have priority.

The international vaccine alliance Gavi is providing $27.5 million for the tests. Another $15 million comes from the Global Fund to Fight AIDS, Tuberculosis and Malaria. With $9.6 million more from UNITAID, WHO has secured all funding for the pilot studies. The work could take four to five years to complete.

GSK developed the vaccine with help from the PATH Malaria Vaccine Initiative, and with financial support from the Bill and Melinda Gates Foundation.

Meanwhile, Sanaria’s malaria vaccine PfSPZ, with an FDA fast-track designation and financial support from government entities and private companies, is also making progress in clinical studies. Previous tests on adults have returned positive data, and the Rockville, Maryland-based vaccine company is trying to determine an optimal dose in phase 1.