SAN FRANCISCO — The highest rates of invasive pneumococcal disease were seen in children younger than 2 years of age in a Massachusetts study, Dr. Katherine K. Hsu reported during a poster session at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The results also showed that black and Hispanic children remain especially vulnerable to nonvaccine-type invasive pneumococcal disease (IPD), compared with white children.
Using microbiology reports of pneumococcal isolates from the Massachusetts Department of Public Health, the researchers identified 357 cases of IPD in children younger than 18 years of age between October 1, 2001, and September 30, 2005. Demographic data were confirmed with follow-up telephone interviews with primary care providers and/or adult caregivers. Incidence rates were derived using Census 2000 denominators.
Dr. Hsu and her associates found that the relative risk of IPD was 15.9 for children younger than 6 months, 16.8 for those aged 6–12 months, and 12.7 for those aged 12–24 months, compared with a relative risk of only 4.5 for children aged 24–60 months. Dr. Hsu did not give any data on older children.
The researchers also found that black and Hispanic children were two times more likely than their white counterparts to have IPD, particularly the nonvaccine type. Dr. Hsu, of the section of pediatric infectious diseases at Boston Medical Center, noted that these differences could not be attributed to unequal vaccination coverage rates. Rather, she said, black and Hispanic children appear to be particularly vulnerable to disease from serotypes not included in the pneumococcal conjugate (PCV7) vaccine.
The study was supported by Wyeth.