Ghana, Kenya and Malawi will pilot the world’s first malaria vaccine from 2018, offering it for babies and children in high-risk areas as part of real-life trials, the World Health Organization said on Monday.

The injectable vaccine, called RTS,S or Mosquirix, was developed by British drugmaker GlaxoSmithKline to protect children from the most deadly form of malaria in Africa.

In clinical trials it proved only partially effective, and it needs to be given in a four-dose schedule, but is the first regulator-approved vaccine against the mosquito-borne disease.

The WHO, which is in the process of assessing whether to add the shot to core package of WHO-recommended measures for malaria prevention, has said it first wants to see the results of on-the-ground testing in a pilot program.

“Information gathered in the pilot will help us make decisions on the wider use of this vaccine,” Matshidiso Moeti, the WHO’s African regional director, said in a statement as the three pilot countries were announced.

“Combined with existing malaria interventions, such a vaccine would have the potential to save tens of thousands of lives in Africa.”

Malaria kills around 430,000 people a year, the vast majority of them babies and young children in sub-Saharan Africa. Global efforts in the last 15 years cut the malaria death toll by 62 percent between 2000 and 2015.

The WHO pilot program will assess whether the Mosquirix’s protective effect in children aged 5 to 17 months can be replicated in real-life.

It will also assess the feasibility of delivering the four doses needed, and explore the vaccine’s potential role in reducing the number of children killed by the disease.

The WHO said Malawi, Kenya and Ghana were chosen for the pilot due to several factors, including having high rates of malaria as well as good malaria programs, wide use of bed-nets, and well-functioning immunization programs.

Each of the three countries will decide on the districts and regions to be included in the pilots, the WHO said, with high malaria areas getting priority since these are where experts expect to see most benefit from the use of the vaccine.

RTS,S was developed by GSK in partnership with the non-profit PATH Malaria Vaccine Initiative and part-funded by the Bill & Melinda Gates Foundation.

The WHO said in November it had secured full funding for the first phase of the RTS,S pilots, with $15 million from the Global Fund to Fight AIDS, Tuberculosis and up to $27.5 million and $9.6 million respectively from the GAVI Vaccine Alliance and UNITAID for the first four years of the program.