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. 2017 Nov 17;12(11):e0187834.
doi: 10.1371/journal.pone.0187834. eCollection 2017.

Vaccine effectiveness against laboratory-confirmed influenza hospitalizations among young children during the 2010-11 to 2013-14 influenza seasons in Ontario, Canada

Sarah A Buchan  1 , Hannah Chung  2 , Michael A Campitelli  2 , Natasha S Crowcroft  1   3   4 , Jonathan B Gubbay  3   4   5 , Timothy Karnauchow  6   7 , Kevin Katz  4   8 , Allison J McGeer  1   4   9 , J Dayre McNally  6 , David Richardson  10 , Susan E Richardson  4   5 , Laura C Rosella  1   2   3 , Andrew Simor  4   11 , Marek Smieja  12 , Dat Tran  5   13 , George Zahariadis  14   15 , Jeffrey C Kwong  1   2   3   16   17
Affiliations

Vaccine effectiveness against laboratory-confirmed influenza hospitalizations among young children during the 2010-11 to 2013-14 influenza seasons in Ontario, Canada

Sarah A Buchan et al. PLoS One. .

Abstract

Uncertainty remains regarding the magnitude of effectiveness of influenza vaccines for preventing serious outcomes, especially among young children. We estimated vaccine effectiveness (VE) against laboratory-confirmed influenza hospitalizations among children aged 6-59 months. We used the test-negative design in hospitalized children in Ontario, Canada during the 2010-11 to 2013-14 influenza seasons. We used logistic regression models adjusted for age, season, and time within season to calculate VE estimates by vaccination status (full vs. partial), age group, and influenza season. We also assessed VE incorporating prior history of influenza vaccination. We included specimens from 9,982 patient hospitalization episodes over four seasons, with 12.8% testing positive for influenza. We observed variation in VE by vaccination status, age group, and influenza season. For the four seasons combined, VE was 60% (95%CI, 44%-72%) for full vaccination and 39% (95%CI, 17%-56%) for partial vaccination. VE for full vaccination was 67% (95%CI, 48%-79%) for children aged 24-59 months, 48% (95%CI, 12%-69%) for children aged 6-23 months, 77% (95%CI, 47%-90%) for 2010-11, 59% (95%CI, 13%-81%) for 2011-12, 33% (95%CI, -18% to 62%) for 2012-13, and 72% (95%CI, 42%-86%) for 2013-14. VE in children aged 24-59 months appeared similar between those vaccinated in both the current and previous seasons and those vaccinated in the current season only, with the exception of 2012-13, when VE was lower for those vaccinated in the current season only. Influenza vaccination is effective in preventing pediatric laboratory-confirmed influenza hospitalizations during most seasons.

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Conflict of interest statement

Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: JBG has received research grants from GSK and Hoffmann-LaRoche for antiviral resistance studies, and from Pfizer Inc. to conduct microbiological surveillance of Streptococcus pneumoniae. AJM has received research funds from GSK and Sanofi-Pasteur. MS has received research grants from Janssen Canada for respiratory virus clinical trials. DT has received research grants from GSK for influenza burden studies and payment for the development of an online course on influenza immunization from Family Physician Airways Group of Canada. All other authors report no conflicts. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Adjusted VE for any vaccination in children aged 24–59 months, by vaccination status during the current and/or the prior influenza seasons, a) by influenza subtype and b) by influenza season.
Vaccine effectiveness estimates are presented for children vaccinated in the current and prior season (circles), the current season only (squares), and the prior season only (triangles).
See this image and copyright information in PMC

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