Officials in Malawi began testing the world’s first malaria vaccine—the RTS,S vaccine developed by GlaxoSmithKline in partnership with the PATH Malaria Vaccine Initiative. The company is donating 10 million doses.

It has taken 30 years to develop the vaccine but WHO officials are optimistic that they may finally make a dent in a disease that kills 435,000 individuals annually, most of them children.

In clinical trials, RTS,S prevented nearly four out of 10 malaria cases and three out of 10 cases of severe malaria.

The new vaccine will be available for Malawian babies and toddlers up to two years old. Officials in Ghana and Kenya will launch programs in the coming weeks.