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Lung Disease & Respiratory Health Center

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Pneumococcal Vaccine: Ripple Effect

Infection Rates Decline Even for Infants Too Young for the Vaccine
WebMD Health News
Reviewed by Louise Chang, MD

April 11, 2006 -- The new pneumococcal vaccine works -- even for kids too young to take it.

The finding is good news for parents of children under 2 months of age. They're too young for the vaccine -- but not too young to get very sick from pneumococcal infection.

Invasive pneumococcal infections in children younger than 2 years have dropped 60% since the vaccine's introduction in February 2000, note Katherine A. Poehling, MD, MPH, of Vanderbilt University, and colleagues. After studying pneumococcal infections in parts of eight U.S. states, the researchers find the benefit extends to children not yet vaccinated.

It's a phenomenon called herd immunity. Herd immunity is when you vaccinate enough people in a community to keep a disease from spreading to unvaccinated people.

"These data are the first to suggest that neonates and infants too young to receive [pneumococcal] vaccine are benefiting from herd immunity," Poehling and colleagues write in the April 12 issue of The Journal of the American Medical Association.

Dangerous Infection

Does this mean you don't have to vaccinate your child? Not really. Once there are enough unvaccinated people in a community, herd immunity disappears. And the disease can come back with a vengeance.

Pneumococcal infections can be very dangerous in children. The Streptococcus pneumoniae bug can cause brain infection, blood infection, pneumonia, ear infection, abscesses, and bone/joint infections.

It's too soon to claim "mission accomplished," however. The pneumococcal vaccine protects against seven strains of S. pneumoniae -- but there are many more of them out there. The researchers warn that scientists must track pneumococcal infections to make sure that a new strain of the bug doesn't emerge.

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