Sometimes, a vaccine is a slam dunk. Take the 97.5-percent-effective Ebola vaccine, for instance, or the 97-percent-effective measles vaccine. Other times, a vaccine is a dud, however, offering little to no protection and clearly destined for the dustbin.
Then there is a third group: the vaccines that fall in the middle. They might protect some, but far from all. The fate of these vaccines is less certain—an open question, in fact.
Such is the case of the world’s first malaria vaccine, which on Tuesday, April 23, was cautiously added to routine vaccinations in the African nation of Malawi as part of a pilot program. Ghana and Kenya will also introduce the vaccine in coming weeks.