title: Impact of ten-valent pneumococcal conjugate vaccination on invasive pneumococcal disease in Finnish children--a population-based study.
abstract: BACKGROUND
  The ten-valent pneumococcal conjugate vaccine (PCV10) was introduced into the Finnish National Vaccination Program (NVP) in September 2010 with a 2+1 schedule (3, 5, 12 months) without catch-up vaccinations. We evaluated the direct and indirect effects of PCV10 on invasive pneumococcal disease (IPD) among children ≤5 years of age during the first three years after NVP introduction.
  
  
  METHODS
  We conducted a population-based, observational follow-up study. The cohort of vaccine-eligible children (all children born June 1, 2010 or later) was followed from 3 months of age until the end of 2013. For the indirect effect, another cohort of older children ineligible for PCV10 vaccination was followed from 2011 through 2013. Both cohorts were compared with season- and age-matched reference cohorts before NVP introduction. National, population-based laboratory surveillance data were used to compare culture-confirmed serotype-specific IPD rates in the vaccine target and reference cohorts by using Poisson regression models.
  
  
  RESULTS
  The overall IPD rate among vaccine-eligible children was reduced by 80% (95%CI 72 to 85); the reduction in vaccine-type IPD was 92% (95%CI 86 to 95). However, a non-significant increase in non-vaccine type IPD was observed. During 2012-2013, we also observed a 48% (95%CI 18 to 69) reduction in IPD among unvaccinated children 2 to 5 years of age, which was mostly attributable to the ten vaccine serotypes.
  
  
  CONCLUSIONS
  This is the first population-based study investigating the impact of PCV10 introduction without prior PCV7 use. A substantial decrease in IPD rates among vaccine-eligible children was observed. A smaller and temporally delayed reduction among older, unvaccinated children suggests that PCV10 also provides indirect protection against vaccine-type IPD. Changes in serotype distribution warrant continuous monitoring of potential increases in non-vaccine serotypes.
authors.affiliation: Department of Vaccination and Immune Protection, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Jokinen
authors.affiliation: Department of Vaccination and Immune Protection, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Rinta-Kokko
authors.affiliation: Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Lotta
authors.initials: L
authors.lastname: Siira
authors.affiliation: Department of Vaccination and Immune Protection, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Arto A
authors.initials: AA
authors.lastname: Palmu
authors.affiliation: Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Virtanen
authors.affiliation: Department of Vaccination and Immune Protection, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Nohynek
authors.affiliation: Department for Promotion of Welfare and Health, Ministry for Social Affairs and Health, Helsinki, Finland.
authors.forename: Anni
authors.initials: A
authors.lastname: Virolainen-Julkunen
authors.affiliation: Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Toropainen
authors.affiliation: Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Helsinki, Finland; Department of Epidemiology, School of Health Sciences, University of Tampere, Tampere, Finland.
authors.forename: J Pekka
authors.initials: JP
authors.lastname: Nuorti
mesh_terms: D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D005387:Finland; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000453:epidemiology / Q000517:prevention & control*; D007223:Infant; D008297:Male; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: C586648:10-valent pneumococcal conjugate vaccine; D022242:Pneumococcal Vaccines