Changes in the composition of the pneumococcal population and in IPD incidence in The Netherlands after the implementation of the 7-valent pneumococcal conjugate vaccine

Vaccine. 2012 Dec 14;30(52):7644-51. doi: 10.1016/j.vaccine.2012.04.021. Epub 2012 Apr 19.


The implementation of nationwide pneumococcal vaccination may lead to alterations in the pneumococcal population due to selective pressure induced by the vaccine. To monitor such changes, pneumococcal isolates causing invasive pneumococcal disease (IPD) before (2004-2005, n=1154) and after (2008-2009, n=1190) the implementation of the 7-valent pneumococcal vaccine (PCV7) in 2006 in the national immunization program (NIP) of The Netherlands were characterized by molecular typing using multiple-locus variable number tandem repeat analysis (MLVA) and capsular sequence typing (CST). The IPD incidence after the implementation of PCV7 in children <5 years of age declined, mainly due to an impressive reduction of cases caused by vaccine serotypes. In the age group of patients ≥5 years of age, the overall IPD incidence remained constant, but the IPD incidence due to vaccine serotypes declined in this age cohort as well, indicating herd immunity. IPD incidence of non-vaccine serotypes 1 and 22F isolates increased significantly and a shift in genetic background of the isolates belonging to these serotypes was observed. In general the composition of the pneumococcal population remained similar after the introduction of PCV7. Both before and after introduction of the vaccine several possible capsular switch events were noticed. We found 4 isolates from the pre-vaccination period in which the serotype 19F capsular locus had been horizontally transferred to a different genetic background. Remarkably, none of the 5 post-vaccination isolates in which we observed possible capsule switch belonged to the 19F serotype, possibly due to vaccine induced pressure. In the post-vaccine implementation period we found no evidence for capsular switch of a vaccine serotype to a non-vaccine serotype, indicating that capsular switch is not the main driving force for replacement. This study provides insights into the effects of nationwide vaccination on the pneumococcal population causing IPD.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacterial Capsules / genetics
  • Child
  • Child, Preschool
  • Female
  • Heptavalent Pneumococcal Conjugate Vaccine
  • Humans
  • Incidence
  • Infant
  • Infant, Newborn
  • Male
  • Meningitis, Pneumococcal / epidemiology*
  • Meningitis, Pneumococcal / microbiology*
  • Middle Aged
  • Minisatellite Repeats
  • Molecular Epidemiology
  • Multilocus Sequence Typing
  • Netherlands / epidemiology
  • Pneumococcal Vaccines / administration & dosage*
  • Pneumococcal Vaccines / immunology*
  • Streptococcus pneumoniae / classification*
  • Streptococcus pneumoniae / genetics
  • Streptococcus pneumoniae / isolation & purification
  • Young Adult


  • Heptavalent Pneumococcal Conjugate Vaccine
  • Pneumococcal Vaccines