Big step in fight against malaria
25 April 2015 Last updated at 12:12 BST
Scientists say they're closer than ever to finding a vaccine to beat the disease malaria.
They say tests in parts of Africa have shown that for the first time, a vaccine could help prevent millions of cases of the deadly disease.
But the vaccine isn't fully effective yet and doctors say that much more hard work needs to be done.
Malaria is carried by mosquitoes and it's a huge problem in countries across Asia, Africa and South America.
Most cases occur in Africa and the disease is particularly harmful to young kids.