title: The effect of pneumococcal conjugate vaccines on the incidence of invasive pneumococcal disease caused by ten non-vaccine serotypes in Denmark.
abstract: BACKGROUND
  Surveillance data on invasive pneumococcal disease (IPD) in Denmark (1999-2014) was analysed regarding the incidence and age-distribution due to ten selected non-PCV serotypes (10-Non-PCV). The effect of PCV-7 and PCV-13 vaccines on the 10-Non-PCV IPD incidence was examined.
  
  
  METHODS
  IPD cases caused by serotypes included in PCV-7, the additional six serotypes included in PCV-13 and 10-Non-PCV serotypes were identified (8, 9N, 11A, 12F, 15A, 22F, 24F, 20, 23B, 33F). The IPD incidence was stratified by three age groups: 0-4 years, 5-64 years and 65+ years.
  
  
  RESULTS
  The predominant IPD cases were caused by serotypes that are not included in PCV-13 (71%), followed by the six additional PCV-13 serotypes. The IPD incidence of serotypes included in the PCV-7 decreased markedly after PCV-7 introduction but are still diagnosed at a low level. The IPD incidence for the 10-Non-PCV serotypes was low for age groups 0-4 years and 5-64 years but high for 65+ years.
  
  
  CONCLUSIONS
  Future vaccinations of the young age group alone with a vaccine targeting some of the 10-Non-PCV serotypes may not elicit the desired effect on herd protection since these serotypes are primarily causing IPD among the elderly. Future pneumococcal vaccination strategies in Denmark may therefore need carriage studies in order to identify among whom the pneumococcal serotypes causing IPD are carried.
authors.affiliation: Neisseria and Streptococcus Reference Laboratory, Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark. Electronic address: hcs@ssi.dk.
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Slotved
authors.affiliation: Neisseria and Streptococcus Reference Laboratory, Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Tine
authors.initials: T
authors.lastname: Dalby
authors.affiliation: Neisseria and Streptococcus Reference Laboratory, Department of Microbiology and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Steen
authors.initials: S
authors.lastname: Hoffmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000627:therapeutic use*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification; D018074:Vaccines, Conjugate / Q000627:therapeutic use; D055815:Young Adult
chemical_list: C538862:13-valent pneumococcal vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
keywords: IPD; Non-PCV serotypes; PCV-13; PCV-7; Streptococcus pneumoniae; Vaccine