Effect of the 13-valent pneumococcal conjugate vaccine on nasopharyngeal carriage by respiratory pathogens among Greenlandic children

ABSTRACT

Background: In 2010, Greenland introduced the 13-valent pneumococcal conjugate vaccine (Prevnar 13®– PCV-13) in the childhood immunisation program. The authors aimed to evaluate the impact of PCV-13 on nasopharyngeal carriage of bacteria frequently associated with respiratory infections in children.

Method: In 2013 a cross-sectional population-based study of nasopharyngeal carriage was conducted among Greenlandic children aged 0–6 years and results were compared with an equivalent study from 2011. Nasopharyngeal swab samples were tested for Streptococcus pneumoniae, non-typeable Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus. Pneumococcal serotyping was performed by Quellung reaction and serotype-specific antisera. Statistical analysis included logistic regression models, adjusting for known risk factors.

Result: A total of 377 nasopharyngeal samples were collected. Overall carriage rate of S. pneumoniae remained unchanged from 2011 to 2013 (51% and 56%, p=0.13), but significant serotype shifts were observed among both vaccinated and unvaccinated children with marked reductions in carriage of vaccine-type pneumococci, counterbalanced by increasing carriage of non-vaccine types. Carriage rate of S. aureus decreased significantly among vaccinated children whereas that of M. catarrhalis increased.

Conclusion: PCV-13 introduction in Greenland is associated with significant changes in nasopharyngeal bacterial carriage. Continued surveillance is warranted to clarify whether these changes are persistent, and affect the pattern of respiratory and invasive diseases in Greenland.

KEYWORDS:

• PCV-13
• carriage
• Inuit
• respiratory infections
• pneumococcus

Acknowledgements

The authors would like to give special thanks for the help and hospitality provided by the chief medical doctors at the Hospital of Tasiilaq, Drs. Hans-Christian Florian Sørensen and Ove Rosing Olsen, respectively, as well as the staff at the two hospitals for logistic assistance. The fieldwork would not have been successful without extensive help from the interpreters Susanne Vid Stein and Antoinette Kuitse. A huge effort was made with analysis of nasopharyngeal samples by the technical laboratory staff at Statens Serum Institut, with special thanks to the laboratory workers Kirsten Olsson, Kirsten Burmeister and Monja Hammer and medical student Jacqueline Mistry. The authors are sincerely grateful for the many participating children and their families for spending time with us and giving us the opportunity to fulfil the study. Finally, the authors are very thankful for the friendly help from the public schools and day-care institutions of Sisimiut and Tasiilaq.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the The Commission of Scientific Research in Greenland co-financed by The Danish Research Council [10-0905576].