Influenza Vaccination and the Risk of COVID-19 Infection and Severe Illness in Older Adults in the United States

Kelly Huang, Shu-Wan Lin, Wang-Huei Sheng, Chi-Chuan Wang

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Received date: 6th December 2020

The COVID-19 pandemic is an urgent threat worldwide with no vaccine available. It is important to evaluate whether influenza vaccination can reduce the risk of COVID-19 infection. This is a retrospective cross-sectional study with claims data from Symphony Health database from July 1, 2019, to June 30, 2020. Participants were adults aged 65 years old or older who had received the influenza vaccine between September 1 and December 31 of 2019. The objective was to measure the odds of COVID-19 infection and severe COVID-19 illness after January 15, 2020 among vaccinated and unvaccinated older adults. The adjusted odds ratio (aOR) of COVID-19 infection risk between the influenza-vaccination group and no-influenza-vaccination group was 0.76 (95% confidence interval (CI), 0.75–0.77). Among COVID-19 patients, the aOR of developing severe COVID-19 illness was 0.72 (95% CI, 0.68–0.76) between the influenza-vaccination group and the no-influenza-vaccination group. When the influenza-vaccination group and the other-vaccination group were compared, the aOR of COVID-19 infection was 0.95 (95% CI, 0.93–0.97), and the aOR of developing a severe COVID-19 illness was 0.95 (95% CI, 0.80–1.13). In conclusion, the influenza vaccine may marginally protect people from COVID-19 infection.

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This is an abstract of a preprint hosted on a preprint server, which is currently undergoing peer review at Scientific Reports. The findings have yet to be thoroughly evaluated, nor has a decision on ultimate publication been made. Therefore, the results reported should not be considered conclusive, and these findings should not be used to inform clinical practice, or public health policy, or be promoted as verified information.

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