SAN FRANCISCO – The incidence of invasive pneumococcal disease among children is declining in the wake of the 2010 introduction of the 13-valent pneumococcal conjugate vaccine, surveillance data suggest.
In New York City during 2011-2012, for example, the incidence of invasive pneumococcal disease (IPD) declined among children under age 5 across all age categories and race/ethnicity groups, Andrea Farnham of the New York City Department of Health and Mental Hygiene reported in a poster at an annual scientific meeting on infectious diseases.
The decline was driven by a reduction in 13-valent pneumococcal conjugate vaccine (PCV13)-type IPD and was temporally associated with the introduction and increased uptake of PCV13 vaccine, she said.
IPD incidence decreased by 70% (from 21.0 to 6.4 cases/100,000) between 2007-2009 and 2011-2012, and PCV13-type IPD incidence decreased 82% (from 15.3 to 2.7 cases/100,000) in that same time period.
The greatest decrease (80%) occurred in children under age 12 months. Decreases were 68% and 62.1% in those aged 12-35 months and 36-59 months, respectively, Ms. Farnham noted.
Another study presented at the meeting showed that 89% of PCV13 serotype disease in Ontario during the second year after the implementation of PCV13 vaccine (2012-2013) occurred in unvaccinated children. Half of the cases (14 of 28) were in children who were not eligible for vaccination, and of the remaining 14, 1 child was unvaccinated, 3 had missed doses, 7 had appropriately received PCV7 vaccine but missed the PCV13 catch-up dose, and 2 received PCV13 vaccine at ages 2 and 4 months but developed IPD at ages 10 and 11 months, respectively, Karen Green, an epidemiologist at Mount Sinai Hospital, Toronto, also reported in a poster.
One apparently healthy 5-year-old developed empyema from serotype 5 disease after receiving age-appropriate vaccination, she noted at the combined annual meetings of the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, the HIV Medicine Association, and the Pediatric Infectious Diseases Society.
The findings suggest that PCV13 vaccination is having a substantial effect on rates of IPD – an effect that could be improved upon with increased vaccine coverage.
A third study suggested that children over age 2 years, in particular, may not be vaccinated appropriately.
In that study, John M. McLaughlin, Ph.D., of Pfizer Specialty Care Medicines Development Group, Collegeville, Penn, showed that although children up to age 1 year had significant reductions in all 13 serotypes covered by the PCV13 vaccine, those aged 2-17 years did not experience a reduction in serotype 19A disease.
Overall, among children aged 0-17 years, the proportion of IPD caused by serotype 19A decreased from 37% in 2008-2009 to 28% in 2010-2011, and the proportion caused by the other 12 serotypes in the PCV13 vaccine decreased from 66% to 48% during the same period.
However, while there was a 44% relative reduction in the proportion of IPD caused by serotypes in the PCV13 vaccine among those aged 0-1 years, there was only a 17% relative reduction in those aged 2-17 years.
"The difference in these two age groups was driven largely by the difference in reduction of the proportion of IPD caused by serotype 19A," he said, explaining that there was a 36% relative reduction in the proportion of IPD caused by serotype 19A among those aged 0-1 years, but no decrease in those aged 2-17 years.
No difference was seen between the 0- to 1-year age group and the 2- to 17-year age group for the remaining serotypes (32% for both groups).
This could be a result of a lack of early indirect effect of vaccination or of the virulence of 19A, or it could be caused by more comorbid disease in the older age group. Comorbidities increased significantly with increasing age, Dr. McLaughlin said, noting that 27% of those aged less than 1 year had comorbid conditions, compared with 32% of those aged 1-2 years, 45% of those aged 3-5 years, and 60% of those aged 6-17 years.
Low PCV13 vaccination rates in older children may also be a factor; in this study, only two children aged 11 years and over had received PCV13 vaccination.
IPD cases in Dr. McLaughlin’s study were identified from eight geographically dispersed children’s hospitals in the U.S. Pediatric Multicenter Pneumococcal Surveillance Study Group. The findings support the Jan. 25, 2013, decision by the Food and Drug Administration to expand the age indication for PCV13 vaccination in children and teens to those aged 6-17 years for prevention of vaccine-type IPD, he concluded (AAP News 2013 March 6 [doi: 10.1542/aapnews.20130306-2]).