A Pneumococcal Carriage Study in Danish Pre-school Children before the Introduction of Pneumococcal Conjugate Vaccination

Zitta B Harboe, Hans-Christian Slotved*, Helle B Konradsen , Margit S Kaltoft
Neisseria and Streptococcus Reference Center, Department of Microbiological Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark

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© Harboe et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Microbiological Surveillance and Research, Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen, Denmark; Tel: +45 32688422; Fax: +45 32683865; E-mail:


We present data on pneumococcal carriage before the introduction of the heptavalent-pneumococcal conjugated vaccine (PCV7) in Denmark. In the pre-PCV7 period, the incidence of invasive pneumococcal disease (IPD) among children younger than 5 years was approximately 25 per 100.000 population, with the highest incidence rates observed in children younger than 2 years of age. The study included 437 children aged 12-72 months attending day care centres (DCC) and was conducted during 48 months. In total, 56% (n=247) of children were pneumococcal carriers with the highest prevalence in children aged 12–23 months (69%), the proportion significantly declining with increasing age. PCV7 serotypes accounted for 33%, PCV10 for 34%, and PCV13 for 57% of all carried isolates. The proportion of serotypes included in the three conjugate vaccines was higher among IPD isolates compared to carrier isolates (range 35– 90%). We found that the frequency of carriage was high among Danish pre-school children attending DCC and serotypes were not frequently covered by PCV7 in the pre-PCV7 period.

Keywords: Children, nasopharyngeal carriage, Streptococcus pneumoniae, serotypes, vaccine.