Influenza vaccine coverage and factors associated with non-vaccination among adults at high risk for severe outcomes: An analysis of the Canadian Longitudinal Study on Aging

Influenza vaccination is recommended in Canada for older adults and those with underlying health conditions due to their increased risk of severe outcomes. Further research is needed to identify who within these groups is not receiving influenza vaccine to identify opportunities to increase coverage. We aimed to 1) estimate influenza non-vaccination prevalence and 2) assess factors associated with non-vaccination among Canadian adults aged [greater than or equal to]65 and adults aged 46-64 with [greater than or equal to]1 chronic medical condition (CMC) due to their high risk of severe influenza outcomes. We conducted a secondary analysis of cross-sectional data collected from 2015-2018 among participants of the Canadian Longitudinal Study on Aging. For both groups of interest, we estimated non-vaccination prevalence and used logistic regression models to identify factors associated with non-vaccination. We report adjusted odds ratios and 95% confidence intervals for the investigated variables. Overall, 29.5% (95% CI: 28.9%, 30.1%) of the 23,226 participants aged [greater than or equal to]65 years and 50.4% (95% CI: 49.4%, 51.3%) of the 11,250 participants aged 46-64 years with [greater than or equal to]1 CMC reported not receiving an influenza vaccination in the past 12 months. For both groups, lack of recent contact with a family doctor and current smoking were independently associated with non-vaccination. Influenza vaccination helps prevent severe influenza outcomes. Yet, half of adults aged 46-64 years with [greater than or equal to]1 CMC and more than one-quarter of all adults aged [greater than or equal to]65 years did not receive a recommended influenza vaccine in the year prior to the survey. Innovation in vaccination campaigns for routinely recommended vaccines, especially among those without annual family doctor visits, may improve coverage. Influenza vaccination coverage among Canadian adults aged 46-64 years with [greater than or equal to]1 CMC and adults aged [greater than or equal to]65 years remains suboptimal. Vaccination campaigns targeting those at high risk of severe outcomes without routine physician engagement should be evaluated to improve uptake.