Influenza Vaccine Effectiveness Against All-Cause Mortality Following Laboratory-Confirmed Influenza in Older Adults, 2010–2011 to 2015–2016 Seasons in Ontario, Canada Journal Articles uri icon

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  • Abstract Background Older adults are at increased risk of mortality from influenza infections. We estimated influenza vaccine effectiveness (VE) against mortality following laboratory-confirmed influenza. Methods Using a test-negative design study and linked laboratory and health administrative databases in Ontario, Canada, we estimated VE against all-cause mortality following laboratory-confirmed influenza for community-dwelling adults aged >65 years during the 2010–2011 to 2015–2016 influenza seasons. Results Among 54 116 older adults tested for influenza across the 6 seasons, 6837 died within 30 days of specimen collection. Thirteen percent (925 individuals) tested positive for influenza, and 50.6% were considered vaccinated for that season. Only 23.2% of influenza test-positive cases had influenza recorded as their underlying cause of death. Before and after multivariable adjustment, we estimated VE against all-cause mortality following laboratory-confirmed influenza to be 20% (95% confidence interval [CI], 8%–30%) and 20% (95% CI, 7%–30%), respectively. This estimate increased to 34% after correcting for influenza vaccination exposure misclassification. We observed significant VE against deaths following influenza confirmation during 2014–2015 (VE = 26% [95% CI, 5%–42%]). We also observed significant VE against deaths following confirmation of influenza A/H1N1 and A/H3N2, and against deaths with COPD as the underlying cause. Conclusions These results support the importance of influenza vaccination in older adults, who account for most influenza-associated deaths annually.


  • Chung, Hannah
  • Buchan, Sarah A
  • Campigotto, Aaron
  • Campitelli, Michael A
  • Crowcroft, Natasha S
  • Dubey, Vinita
  • Gubbay, Jonathan B
  • Karnauchow, Timothy
  • Katz, Kevin
  • McGeer, Allison J
  • McNally, J Dayre
  • Mubareka, Samira
  • Murti, Michelle
  • Richardson, David C
  • Rosella, Laura C
  • Schwartz, Kevin L
  • Smieja, Marek
  • Zahariadis, George
  • Kwong, Jeffrey C

publication date

  • September 7, 2021