Pneumonia comes in two flavors: viral and bacterial. So you'd think vaccinating against bacteria wouldn't affect the chances of getting viral pneumonia. But you'd be wrong, say a big group of vaccine researchers.

What the researchers wanted to know: Does vaccinating against pneumococcal bacteria help prevent viral pneumonias?

What they did: Nearly 40,000 children in Soweto, South Africa, were enrolled in the study between 1998 and 2000 and randomly assigned to get either the pneumococcal virus or placebo. (All of the children got all the other childhood vaccines.) This article used data on the children through mid-November, 2001. Children who were hospitalized for bronchiolitis or pneumonia were checked for respiratory viral infections.

What they found: Children who'd had the vaccine were 30 percent less likely to get viral pneumonia, even though the vaccine is against bacteria, not viruses.

What the study means to you: It seems that bacteria can be involved even in viral pneumonia, so vaccinating against the Streptococcus pneumoniae bacteria seems to help ward off viral pneumonia, too—not just bacterial pneumonia.

Caveats: The study only looked at children, so you can't tell if this strategy would work on adults.

Find out more: The CDC has an interactive tool that tells you what vaccines your child needs when.

Read the article: Madhi, S.A., Klugman, K.P., and The Vaccine Trialist Group. "A role for Streptococcus pneumoniae in Virus-Associated Pneumonia." Nature Medicine. August 1, 2004, Vol. 10, pp. 811-813.

Abstract online: http://www.nature.com/