Assessing the impact of COVID-19 infection on vaccine uptake during Omicron outbreaks

Abstract

Introduction

During the COVID-19 pandemic, how daily incidence affected vaccination dynamics remains largely unknown. The study aimed at assessing the association between daily infection and daily vaccination during Omicron outbreaks. We collected the daily number of cases and vaccine booster doses from seven countries/regions, including Hong Kong, Japan, Malaysia, South Korea, Singapore, Thailand and New Zealand in the Pacific Asian region between October 2021 and October 2022.

Material and Methods

Dynamic Time Warping (DTW) and the linear regression model have been used to analyze the time-series diagrams of infection and vaccination to determine whether there was a trend of interaction between them. A daily number of tests performed and daily stringency index were used as potential confounders.

Results

DTW showed that the dynamics of infection and vaccination were similar. The regression model demonstrated that the relationship between daily infection and vaccine booster doses was positive in Hong Kong, South Korea, Singapore and New Zealand but negative in Japan, Malaysia and Thailand. Further analysis showed that countries with a positive relationship had lower vaccine booster rates when booster doses were available.

Discussion

A positive relationship between infection and vaccination appeared in most of the study countries with higher vaccine hesitancy. A certain amount of people might be delayed in vaccine uptake until they were aware of a higher risk of infection. The limitation of this study is that we only analyzed the Asia-Pacific region. In the future, we hope to develop more generalizable models to assess the relationship between infection and vaccination. Moreover, the study can help the government increase vaccine uptake.