> The latest study does have drawbacks. It is based on a small number of cases among young and healthy adults, which limits its application, says Andrew Fiore-G

> The latest study does have drawbacks. It is based on a small number of cases among young and healthy adults, which limits its application, says Andrew Fiore-Gartland, a biostatistician at the Fred Hutchinson Cancer Research Center in Seattle, Washington. More studies from vaccine trials are expected soon, he says.