Effect of Vaccination on Pneumococci Isolated from the Nasopharynx of Healthy Children and the Middle Ear of Children with Otitis Media in Iceland

J Clin Microbiol. 2018 Nov 27;56(12):e01046-18. doi: 10.1128/JCM.01046-18. Print 2018 Dec.


Vaccination with pneumococcal conjugate vaccines (PCVs) disrupts the pneumococcal population. Our aim was to determine the impact of the 10-valent PCV on the serotypes, genetic lineages, and antimicrobial susceptibility of pneumococci isolated from children in Iceland. Pneumococci were collected between 2009 and 2017 from the nasopharynges of healthy children attending 15 day care centers and from the middle ears (MEs) of children with acute otitis media from the greater Reykjavik capital area. Isolates were serotyped and tested for antimicrobial susceptibility. Whole-genome sequencing (WGS) was performed on alternate isolates from 2009 to 2014, and serotypes and multilocus sequence types (STs) were extracted from the WGS data. Two study periods were defined: 2009 to 2011 (PreVac) and 2012 to 2017 (PostVac). The overall nasopharyngeal carriage rate was similar between the two periods (67.3% PreVac and 61.5% PostVac, P = 0.090). Vaccine-type (VT) pneumococci decreased and nonvaccine-type (NVT) pneumococci (serotypes 6C, 15A, 15B/C, 21, 22F, 23A, 23B, 35F, and 35B) significantly increased in different age strata post-PCV introduction. The total number of pneumococci recovered from ME samples significantly decreased as did the proportion that were VTs, although NVT pneumococci (6C, 15B/C, 23A, and 23B) increased significantly. Most serotype 6C pneumococci were multidrug resistant (MDR). Serotype 19F was the predominant serotype associated with MEs, and it significantly decreased post-PCV introduction: these isolates were predominantly MDR and of the Taiwan19F-14 PMEN lineage. Overall, the nasopharyngeal carriage rate remained constant and the number of ME-associated pneumococci decreased significantly post-PCV introduction; however, there was a concomitant and statistically significant shift from VTs to NVTs in both collections of pneumococci.

Keywords: Iceland; Streptococcus pneumoniae; carriage; epidemiology; molecular epidemiology; otitis media; pneumococcus; vaccination; vaccine.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Carrier State / epidemiology
  • Carrier State / microbiology*
  • Child
  • Child, Preschool
  • Drug Resistance, Multiple, Bacterial
  • Ear, Middle / microbiology
  • Genome, Bacterial / genetics
  • Humans
  • Iceland / epidemiology
  • Infant
  • Infant, Newborn
  • Microbial Sensitivity Tests
  • Multilocus Sequence Typing
  • Nasopharynx / microbiology
  • Otitis Media / epidemiology
  • Otitis Media / microbiology*
  • Pneumococcal Infections / epidemiology
  • Pneumococcal Infections / microbiology*
  • Pneumococcal Infections / prevention & control
  • Pneumococcal Vaccines / administration & dosage
  • Pneumococcal Vaccines / adverse effects
  • Serogroup
  • Serotyping
  • Streptococcus pneumoniae / classification
  • Streptococcus pneumoniae / drug effects
  • Streptococcus pneumoniae / genetics
  • Streptococcus pneumoniae / isolation & purification*
  • Vaccination / adverse effects*


  • 10-valent pneumococcal conjugate vaccine
  • Anti-Bacterial Agents
  • Pneumococcal Vaccines