Comparison of seasonal influenza vaccine hesitancy among young adults at a Hong Kong university before and after the start of the COVID-19 pandemic: A repeated cross-sectional study

Vaccine hesitancy (VH) among young adults limited seasonal influenza vaccine (SIV) uptake in Hong Kong. The impact of the COVID-19 pandemic on this issue remains unclear. A repeated cross-sectional study was performed on 269 young adults aged 18 to 35 at a Hong Kong's university during two seasons: pre-COVID-19 (September 30, 2019, to April 1, 2020, with 130 participants) and during-COVID-19 (March 29, 2021, to May 2, 2021, with 139 participants). We developed our questionnaire based on the Health Belief Model (HBM) and included peer influence. The best-fitting logistic regression model selected by the chi-square test and Akaike Information Criterion (AIC), was used to assess the association between selected factors and VH in both periods. From the pre- to during-COVID-19 pandemic, the proportion of participants exhibiting vaccine hesitancy increased from 43.8 % to 62.6 %. Perceived vaccine side effects, vaccine efficacy and peers' vaccination status became significant with odds ratio of 3.941 (95 % Confidence Interval (CI) [1.27, 14.36]), 0.1344 (95 % CI [0.02, 0.56]) and 0.1147 (95 % CI [0.02, 0.52]), respectively. A comprehensive approach that includes effective communication about vaccine safety and efficacy is crucial. Additionally, the vaccination status of peers may play an important role in vaccine promotion among young adults in Hong Kong.