Adults may owe kids a “thank you” for helping them avoid pneumonia and related diseases.

Fewer adults were reported to have pneumococcal disease in recent years, a new study shows. That overlaps with the introduction of a new vaccine for kids. Vaccinated children may be less likely to get sick and give that illness to adults, the researchers write.

Coincidence? Probably not, write researchers in The Journal of the American Medical Association.

Pneumococcal disease is an infection caused by the bacterial organism Streptococcus pneumoniae. It is typically associated with infection of the lung (pneumonia); it also causes other infections such as ear and sinus infections, meningitis (infection of the covering around the brain), and blood infection.

More people per year in the U.S. die from pneumococcal disease than all other vaccine-preventable diseases combined, according to the CDC.

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Drop in Pneumonia

The researchers included Catherine Lexau, PhD, MPH, of Minnesota’s health department.

Lexau and colleagues tracked invasive pneumococcal disease in adults before and after a pneumococcal vaccine for infants and young children was introduced in 2000.

The kids’ pneumococcal vaccine is called the conjugate vaccine, or PCV-7. It works against seven types of pneumococcal bacteria.

Adults get a different pneumococcal vaccine, called the PPV23, which works against 23 types of pneumococcal bacteria. The young, old, and ill are particularly vulnerable to pneumococcal infection.

The researchers tracked cases of invasive pneumococcal disease in adults age 50 and older in eight U.S. cities. They checked numbers from 1998-1999 and 2002-2003.

They found a 28 percent drop in overall reported cases of adults with invasive pneumococcal disease between the two time periods.

They also found that reported cases of disease caused by the seven types of pneumococcal bacteria covered by the children’s PCV-7 vaccine decreased by 55 percent. There was no change seen with the other 16 types covered by the adult PPV-23 vaccine.

The most common invasive pneumococcal diseases included invasive pneumonia, blood infection (bacteremia), and meningitis, note the researchers.

Their conclusion: the kids’ vaccine likely benefited adults.

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Kids Paved the Way

Why did grown-ups benefit? Vaccinated children may be less likely to get sick and give that illness to adults, the researchers write. They note that the PCV-7 vaccine also helps to hinder transmission of the bacteria in the general public.

Healthy adults seemed to benefit most. The numbers of infected adults with underlying medical conditions that make them more susceptible to infection increased during the study.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Lexau, C. The Journal of the American Medical Association, Oct. 26, 2005; vol 294: pp 2043-2051. News release, JAMA/Archives. CDC.