Clin Infect Dis . Influenza vaccine effectiveness against all-cause mortality following laboratory-confirmed influenza in older adults, 2010-2011 to 2015-2016 seasons in Ontario, Canada

[tetano]

Clin Infect Dis


. 2020 Dec 23;ciaa1862.
doi: 10.1093/cid/ciaa1862. Online ahead of print.
Influenza vaccine effectiveness against all-cause mortality following laboratory-confirmed influenza in older adults, 2010-2011 to 2015-2016 seasons in Ontario, Canada


Hannah Chung ¹ , Sarah A Buchan ^{1 2 3} , Aaron Campigotto ^{4 5} , Michael A Campitelli ¹ , Natasha S Crowcroft ^{1 3 6 7} , Vinita Dubey ^{3 8} , Jonathan B Gubbay ^{2 4 7} , Timothy Karnauchow ^{9 10} , Kevin Katz ¹¹ , Allison J McGeer ^{3 7 12} , J Dayre McNally ⁹ , Samira Mubareka ¹³ , Michelle Murti ^{2 3} , David C Richardson ¹⁴ , Laura C Rosella ^{1 2 3} , Kevin L Schwartz ^{1 2 3} , Marek Smieja ¹⁵ , George Zahariadis ^{5 16} , Jeffrey C Kwong ^{1 2 3 6 17 18}



Affiliations

• PMID: 33354709
• DOI: 10.1093/cid/ciaa1862

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, 6,837 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%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.

Keywords: Influenza vaccine; mortality; older adults; vaccine effectiveness.