Pneumococccal Conjugate Vaccine, the Netherlands | CDC EID

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Volume 16, Number 5–May 2010
Research
Effects of Pneumococcal Conjugate Vaccine 2 Years after Its Introduction, the Netherlands
Gerwin D. Rodenburg,1 Sabine C. de Greeff,1 Angelique G.C.S. Jansen, Hester E. de Melker, Leo M. Schouls, Eelko Hak, Lodewijk Spanjaard, Elisabeth A.M. Sanders,2 and Arie van der Ende2
Author affiliations: Wilhelmina Children's Hospital/University Medical Center, Utrecht, the Netherlands (G.D. Rodenburg, A.G.C.S Jansen, E. Hak, E.A.M. Sanders); National Institute for Public Health and the Environment, Bilthoven, the Netherlands (S.C. de Greeff, H.E. de Melker, L.M. Schouls); University Medical Center, Groningen, the Netherlands (E. Hak); and Netherlands Reference Laboratory for Bacterial Meningitis, Amsterdam, the Netherlands (L. Spanjaard, A. van der Ende)

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Abstract
In the Netherlands, the 7-valent pneumococcal conjugate vaccine (PCV-7) was implemented in a 3+1-dose schedule in the national immunization program for infants born after April 1, 2006. To assess the vaccine's effectiveness, we compared disease incidence before and after vaccine implementation (June 2004–June 2006 and June 2006–June 2008, respectively). We serotyped 2,552 invasive pneumococcal isolates from throughout the Netherlands, covering 25% of the country's population. Clinical characteristics were extracted from hospital records. After June 2006, vaccine-serotype invasive pneumococcal disease (IPD) decreased 90% (95% confidence interval [CI] 68%–97%) in children age eligible for PCV-7; simultaneously, however, non–vaccine-serotype IPD increased by 71% (not significant), resulting in a 44% total net IPD reduction (95% CI 7%–66%). IPD rates did not change for other age groups. In the Netherlands, PCV-7 offered high protection against vaccine-serotype IPD in vaccinated children, but increases of non–vaccine-serotype IPD reduced net vaccine benefits.
Streptococcus pneumoniae is a leading cause of invasive infections, such as meningitis, septicemia, and bacteremia, and of more common respiratory tract infections, such as pneumonia and otitis media. Young children and elderly persons are at particularly high risk for pneumococcal infection (1). In the United States, the introduction in 2000 of the CRM197-conjugated 7-valent pneumococcal vaccine (PCV-7) resulted in a 77% reduction in 2005 of invasive pneumococcal disease (IPD) in children <5 years of age from IPD rates reported in 1998–1999 (2). IPD rates in children decreased mostly within the first 2 years after introduction of PCV-7; leveled off in 2002; and then stabilized, despite an ongoing decrease of vaccine-serotype IPD, due to a gradual increase of non–vaccine-serotype IPD, particularly serotype 19A (2,3). In addition, use of the vaccine in children was associated with reduced IPD rates for unvaccinated age groups, which resulted from reduced nasopharyngeal colonization of vaccine-serotype S. pneumoniae in vaccinated children and concomitant reduced transmission (4,5). The cost effectiveness of herd immunity conferred by the conjugate vaccine in the United States prompted implementation of the vaccine in the Netherlands (6).

Data from the United States concerning both direct and indirect vaccine benefit, however, cannot be translated indiscriminately to European countries because of several major differences. Vaccine-serotype coverage by PCV-7 was lower in European countries (60%–70%) than in the United States (>80%) (7), which may leave more room for non–vaccine-serotype replacement in European countries. Second, in the Netherlands (as in most European countries), baseline IPD incidence rates are based mainly on culture-confirmed cases in hospitalized children, resulting in markedly lower IPD incidence rates for young children in the Netherlands than for those in the United States, where blood samples are cultured for more patients. Before introduction of PCV-7 in the Netherlands, overall IPD rates were 35 cases/100,000 children <2 years of age, of which 15 cases/100,000 children were meningitis (1). In contrast, in the United States, IPD incidence before introduction of PCV-7 peaked at 188 cases/100,000 children <2 years of age in 1998–1999 (5), and 10 cases/100,000 children in that age group were meningitis (8).

Consequently, introduction of PCV-7 may have affected IPD incidence in European countries differently than in the United States. (9). To assess the effectiveness of PCV-7 on IPD in the Netherlands, we evaluated the incidence and clinical syndromes of IPD in PCV-7–vaccinated and –unvaccinated children and in other age groups during the first 2 years after implementation of PCV-7.

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Suggested Citation for this Article
Rodenburg GD, de Greeff SC, Jansen AGCS, de Melker HE, Schouls LM, Hak E et al. Effects of pneumococcal conjugate vaccine 2 years after its introduction, the Netherlands. Emerg Infect Dis [serial on the Internet]. 2010 May [date cited].
http://www.cdc.gov/EID/content/16/5/816.htm

DOI: 10.3201/eid1605.091223