ABSTRACT
Introduction: We aim to explore the association between seasonal influenza vaccine behavior (from 2018 Southern Hemisphere to 2020/2021 Northern Hemisphere influenza seasons) and COVID-19 vaccine uptake among healthcare workers. Material and Methods: This study used electronic vaccination records of staff who have worked in a tertiary hospital for at least 3 years. Multivariable logistic regression was used to predict early adopters of COVID-19 vaccine (receive the vaccine within the first month of vaccine roll-out). We used Cox proportional hazards models to estimate hazard ratios (HRs) for the probability of COVID-19 vaccine uptake at 260 days (from 30 Dec 2020 to 15 Sept 2021). Results: Of the 6121 staff, 81% were females, 39% were nurses, 84% had at least three past influenza vaccines and 12% had one to two past influenza vaccines. The COVID-19 vaccine uptake was 96%. Staff who had >=3 influenza vaccines (OR 3.3, 95%CI 2.6-4.1) and staff who had 1-2 influenza vaccines (OR 1.4, 95%CI 1.1-1.9), had higher odds of COVID-19 vaccine uptake in the first month of vaccine roll-out compared to those who did not receive any, after adjustment for age, gender, years working in hospital and healthcare groups. At 260 days, HRs for COVID-19 vaccine uptake among staff who received >=3 past doses of influenza vaccines and staff who received 1-2 doses of influenza vaccines, compared to those without, were 2.0 (95%CI 1.7-2.3) and 1.3 (95%CI 1.1-1.5) respectively. Conclusion: Seasonal influenza vaccine uptake is a strong predictor of COVID-19 vaccine adoption and should be promoted even when there is no epidemic.