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Trends in Asymptomatic Nasopharyngeal Colonization With Streptococcus pneumoniae After Introduction of the 13-valent Pneumococcal Conjugate Vaccine in Calgary, Canada

Ricketson, Leah J. MSc*; Wood, Melissa L. BSc; Vanderkooi, Otto G. MD; MacDonald, Judy C. MD§¶; Martin, Irene E. BSc‖**; Demczuk, Walter H.B. BSc‖**; Kellner, James D. MD; for the Calgary Streptococcus pneumoniae Epidemiology Research (CASPER) investigators

Pediatric Infectious Disease Journal: July 2014 - Volume 33 - Issue 7 - p 724–730
doi: 10.1097/INF.0000000000000267
Original Studies

Background: We previously reported serotype-specific trends in pneumococcal nasopharyngeal colonization soon after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in mid-2002. Our current aim is to describe later trends after PCV7 and early trends after PCV13 vaccine introduction in 2010.

Methods: The Calgary Area Streptococcus pneumoniae Epidemiology Research team conducted 10 point-prevalence surveys of pneumococcal nasopharyngeal colonization in healthy children aged 12 and 18 months and 4.5 years biannually from 2003 to 2005 (previously reported) and annually in 2006, 2010, 2011 and 2012.

Results: For surveys conducted during 2010–2012, the proportion colonized was 13.2% compared with 19.9% in surveys conducted during 2003–2006 (P < 0.001). Vaccination with 2 or more doses of PCV7 or PCV13, older age and recent antibiotic use reduced the odds of colonization with any pneumococcus. By 2012, 94% of all isolates were nonvaccine serotypes with 11A, 15A/B/C, 22F, 23A/B and 35B/F representing 75% of all isolates.

Conclusions: Pneumococcal nasopharyngeal colonization has changed profoundly since the introduction of conjugate vaccines and overall colonization by pneumococcus has declined in recent years. By 2012, nonvaccine serotypes have nearly completely replaced vaccine serotypes. The impact on clinical disease remains to be seen.

From the *Department of Pediatrics, University of Calgary, Calgary; Faculty of Medicine, University of Alberta, Edmonton, Alberta; Department of Pediatrics and Alberta Children’s Hospital Research Institute; §Population and Public Health, Alberta Health Services; Department of Community Health Sciences, University of Calgary, Calgary, Alberta; Bacterial and Enteric Diseases Program, National Microbiology Laboratory, Winnipeg; and **Public Health Agency of Canada, Canadian Science Centre for Human and Animal Health, Winnipeg, Manitoba, Canada.

Accepted for publication December 23, 2013.

This work and the CASPER project are supported in part by unrestricted grants from Pfizer Canada and the Alberta Children’s Hospital Research Institute to J.D.K., O.G.V. and J.C.M. The authors have no other funding or conflicts of interest to disclose.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (www.pidj.com).

Address for correspondence: James D. Kellner, MD, Alberta Children’s Hospital, 2888 Shaganappi Trail NW Calgary, Alberta, T3B 6A8, Canada. E-mail: Jim.Kellner@albertahealthservices.ca.

© 2014 by Lippincott Williams & Wilkins, Inc.