NEW YORK (Reuters Health) Apr 11 - Since the introduction of a heptavalent pneumococcal conjugate vaccine (PCV7) in 2000 and its recommendation for all children 2-23 months old, rates of invasive pneumococcal disease among young infants have declined, new research suggests.

Previous reports have linked PCV7 use with a drop in IPD rates among children younger than 2 years of age. However, it was unclear if childhood PCV7 immunization reduced disease rates among infants who were too young to receive PCV7 themselves, namely those who were just a few months old.

In the present study, reported in the Journal of the American Medical Association for April 12, Dr. Katherine A. Poehling, from Vanderbilt University School of Medicine in Nashville, and colleagues assessed IPD rates among infants, 0 to 90 days of age, before and after the introduction of PC7V.

In the eight states studied, 89 cases of IPD occurred before PCV7 introduction and 57 occurred afterward. The bulk of these cases - 64% -- involved isolated bacteremia.

With the introduction of PCV7, the average rate of IPD among young infants fell 40% from 11.8 to 7.2 cases per 100,000 live births. The reduction was most pronounced for black infants, falling from 17.1 to 5.3 cases per 100,000 live births (p = 0.001). By contrast, the decline seen among white infants was not statistically significant.

Use of PCV7 was associated with a drop in rates of PCV7-serotype isolates, but seemed to have no effect on rates of non-PCV7 serotypes.

"Our data provide further evidence that PCV7 has resulted in herd immunity because neonates and young infants have had a significant decrease in IPD rates, although they are too young to receive a full series of PCV7," the authors conclude.

Reuters Health Information 2006. © 2006 Reuters Ltd.
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