Strep Vaccine for Kids Cuts Pneumonia Even Among Adults

NASHVILLE, Tenn., April 6 -- Evidence continues to mount that the use of the new pneumococcal conjugate vaccine is sharply reducing the rate of pneumonia in young children -- and even in adults who have never been vaccinated.

At the end of the 2004, all-cause hospital admission for pneumonia in children under the age of two years had fallen 39%, compared with expected rates based on the years before the vaccine's introduction, found Carlos Grijalva, M.D., of Vanderbilt here, and colleagues and the CDC.

The decline in all-cause pneumonia admissions was 506 per 100,000 children under two, and represented 41,000 pneumonia admissions prevented in 2004, Dr. Grijalva and colleagues reported in the April 7 issue of The Lancet.

Moreover, all-cause pneumonia admissions fell 26% among adults ages 18 to 39, which was statistically significant at P=0.021. Because people in that age group are likely to be parents of young children, the researchers said "they could have benefited from reduced exposure to pneumococci because their children were vaccinated."

The finding came from an analysis of hospital admission rates, as estimated by the Nationwide Inpatient Sample, the largest inpatient database available in the country.

The researchers looked at admission rates for all-cause and pneumococcus-specific pneumonia in the years 1977 through 1999, as well as rates of admission for dehydration, which served as a comparison.

The year 2000, in which the vaccine was introduced, was excluded, and Dr. Grijalva and colleagues calculated rates of admission for the years 2001 through 2004.

Compared with the expected rates, based on the earlier years:

• The rate of admissions for all-cause pneumonia per 100,000 children under two was 790.9, down by 505.9 from the expected rate.
• The rate for pneumococcal disease was 9.2, down by 17.1 from the expected rate.
• Among adults aged 18 through 39, the rate of admissions for all-cause pneumonia per 100,000 was 77.9, down by 27.4 from the expected rate.
• Admissions for dehydration were either stable or slightly increased for all age groups, except adults over 65, where the rate was 736.9 per 100,000, down 140.5 from the expected rate.

The findings are consistent with limited post-marketing surveillance studies, Dr. Grijalva and colleagues said, and extend the efficacy estimates derived from clinical trials of the vaccine by demonstrating a "herd effect" among non-vaccinated adults.

The report comes just days after researchers reported on another aspect of the vaccine -- its effect on otitis media. In that study, they found that the main beneficiaries of the vaccine were those prone to repeated ear infections. (Strep Vaccine Benefits Kids Prone to Ear Infection)

"The reduction in all-cause pneumonia in vaccinated and unvaccinated populations illustrates again how the value of the vaccine has far exceeded expectations," said Orin Levine, Ph.D., and Felicity Cutts, M.D., Ph.D., both of the Global Alliance for Vaccines and Immunization, in an accompanying editorial.

They wrote that the findings are important because estimates of the value of the vaccine, seen in clinical trials, were limited to the effect on vaccinated children.

Although clinical trials remain important to judge the efficacy of new interventions, they said, other methods of analysis can "uncover effects that might be missed by the venerable randomized trial."

The research was funded by the CCD, the Association for Prevention Teaching and Research, and the Agency for Healthcare Research and Quality.