Some human malarias, including the Plasmodium vivax strain widespread in Asia, have cycles in which parasites periodically increase, making victims sick again.

They showed that the mutation definitely reduces the number of malaria-causing Plasmodium vivax parasites, lessening the severity of the disease.

Then there is the next goal, said Cohen - a vaccine against Plasmodium vivax, the parasite that causes most cases of malaria in Asia.