Effectiveness of thirteen-valent pneumococcal conjugate vaccine to prevent serotype 3 invasive pneumococcal disease in Quebec in children, Canada.

In the province of Quebec, Canada, a 2 + 1 dose pneumococcal conjugate vaccine (PCV) program for children was implemented in 2004. PCV7 was replaced by PCV10 in 2009, by PCV13 in 2011 and by PCV10 in 2018, without catch-up in all instances. The objective was to estimate PCV13 effectiveness to prevent serotype 3 invasive pneumococcal disease in children aged less than 5 years, using 2010-2018 mandatory notification and laboratory surveillance data, an indirect cohort design and multivariate logistic regression models. A total of 29 cases of serotype 3 and 290 non-vaccine serotype cases as controls were analysed. Overall vaccine effectiveness (≥1 dose) was estimated at 59% [-39% to 88%]. During the first year after the last dose effectivness was 88% [47% to 97%] whereas no protection was observed thereafter. There was no trend towards increased effectiveness with the number of doses. PCV13 protection against serotype 3 IPD seems to be short-lived.

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Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Potential conflicts of interest The sponsor had no role in the design and conduct of the study, collection, management, analysis, and interpretation of the data, and preparation, review, and approval of the manuscript. This research received no other external financial or non-financial support. All co-authors have nothing to disclose.