The first pneumonia vaccine for babies was approved in 2000 and is now recommended for all children under age 2. It fights infections caused by pneumococcus bacteria, including pneumonia, blood poisoning, meningitis and ear infections.

Researchers say they believe the vaccine, Prevnar, reduced the rate of blood infections and meningitis in children under 2 by nearly 70 percent.

"The vaccine is working. It is not only preventing diseases in high-risk children but also in their families," said Dr. Cynthia Whitney, who led the study for the Centers for Disease Control and Prevention.

How many infants have been immunized isn't known yet, but the vaccine has been widely adopted.

The findings appear in today's New England Journal of Medicine, along with a three-year study of an older pneumonia vaccine recommended for everyone over 65. In that study of 47,365 people, the vaccine cut the risk of serious blood infections almost in half, but offered no protection against pneumonia, reflecting some previous research in the elderly.

"There's a benefit of the vaccine. It's just the benefit doesn't extend to prevention of pneumonia from what we can tell," said Dr. Lisa A. Jackson, who led the CDC-funded research at the Group Health Cooperative.

Pneumococcus bacteria is carried in the nose and throat of healthy people, and is spread from person to person. The very young and the elderly are most vulnerable, as well as people with medical conditions that weaken their immune system.

Until 2000, pneumococcal infections resulted in up to 135,000 annual hospitalizations for pneumonia and 60,000 cases of blood infections, including 3,300 cases of meningitis, according to the CDC.

Those numbers are changing because of the new infant vaccine. The CDC study examined the vaccine's impact by tracking the more serious pneumococcal infections -- blood poisonings and meningitis -- in seven areas of the country covering 16 million people.

This story appeared in The Daily Herald on page A12.