Every year, malaria kills more than 400,000 people, most of them children. There has been significant progress against the disease in the past few decades — death rates have fallen nearly in half since 2000 — but there’s still a long way to go.

For decades, researchers have been working on developing a vaccine. It hasn’t been easy. Malaria, a parasite infection, is hard to vaccinate against, and many attempted vaccines haven’t produced durable immunity.

But progress is happening. On Wednesday, the World Health Organization (WHO) announced it has given its stamp of approval to a vaccine against malaria for children for the first time, after encouraging results from a pilot study that has reached hundreds of thousands of children across parts of sub-Saharan Africa since 2019. The vaccine, called Mosquirix and made by GlaxoSmithKline, is far from perfect — it produces about a 30 percent reduction in severe malaria in fully vaccinated children, which is lifesaving but smaller than would be hoped for.