The bacteria Streptococcus pneumoniae cause a lot of problems, especially for infants and toddlers. Researchers at Vanderbilt University, the University of Rochester, and the Centers for Disease Control and Prevention looked at what the impact of the pneumococcal conjugate vaccine has been on rates of pneumonia and ear infections, two of the diseases caused primarily by these bacteria.

What the researchers wanted to know: Does vaccinating children with PCV, the pneumococcal conjugate vaccine, reduce the rates of diseases caused by pneumococcal bacteria?

What they did: The researchers compared disease rates in children on Medicaid in Tennessee and in three health plans in upstate New York before and after the vaccine started being given in 2000-2001.

What they found: Rates of ear infections, pneumonia, and worse infections declined after the vaccine came into use. Ear infections went down by 6 percent in the Tennessee children and 20 percent in the children from New York.

What the study means to you: The vaccine seems to work.

Caveats: The researchers didn't look at which kids had gotten the vaccine, but they knew when it started being given. And they can't know whether the disease rates went down because of the vaccine or because of some giant coincidence—but it would be a pretty giant coincidence.

Find out more: Get childhood vaccination schedules from the Centers for Disease Control & Prevention.

An article from the Food and Drug Administration explains vaccine safety.

Read the article: Poehling, K.A., et al. "Population-Based Impact of Pneumococcal Conjugate Vaccine in Young Children." Pediatrics. Sept. 2004, Vol. 114, No. 3, pp. 755-761.

Abstract online: http://pediatrics.aappublications.org