Estimation of COVID-19 Vaccine Effectiveness against Mortality During April to December 2022 of COVID Infections in Taiwan Öffentlichkeit

Abstract

Taiwan's response to the COVID-19 pandemic underwent a significant shift in strategy, transitioning from stringent non-pharmaceutical interventions (NPIs) established in January 2020 to prioritizing mass vaccination as the Omicron variant emerged in April 2022. This thesis presents findings from an observational study conducted in Taiwan from April to December 2022, aimed at evaluating the effectiveness of the mass vaccination campaign against the Omicron BA.2 variant. The study employed Poisson regression models to estimate vaccine effectiveness against COVID-19 mortality in the population. Vaccine effectiveness was assessed across two distinct time periods: April 19th, 2022, to August 19th, 2022, designated as Wave 1, and August 20th, 2022, to December 4th, 2022, designated as Wave 2, corresponding to peaks in infections and deaths, comparing vaccinated individuals with unvaccinated counterparts and varying numbers of vaccine doses received. The analysis revealed a substantial reduction in COVID-19 mortality post-vaccination, with an overall vaccine effectiveness of 91.0% (95% confidence interval 90.7%-91.3%) estimated for the study period. Notably, vaccine effectiveness for individuals receiving two doses of the vaccine exhibited higher efficacy compared to those receiving a single dose, with vaccine effectiveness for Wave 2 surpassing that of Wave 1 across all comparison groups. Comparisons with similar studies conducted in Israel and Hong Kong highlighted Taiwan's vaccine effectiveness alignment with Hong Kong's findings. Discrepancies in vaccine effectiveness outcomes were attributed to variations in vaccine compositions and dominant virus strains. This research contributes valuable insights into the effectiveness of Taiwan's mass vaccination campaign amidst evolving pandemic dynamics, informing future public health interventions and policy decisions. 

Table of Contents

Chapter 1 Introduction........................................................................................................... 1

Chapter 2 Literature Review ................................................................................................. 4

2.1 Vaccine efficacy.............................................................................................................. 4

2.2 Vaccine effectiveness...................................................................................................... 4

Chapter 3 Manuscript........................................................................................................... 10

3.1 Introduction................................................................................................................... 10

3.2 Methods......................................................................................................................... 10

3.2.1 Study design and population............................................................................ 11

3.2.2 Statistical Analysis........................................................................................... 12

3.3 Results........................................................................................................................... 13

3.4 Discussion ..................................................................................................................... 16

Chapter 4 Conclusion ........................................................................................................... 21

Chapter 5 Implications ......................................................................................................... 22

References............................................................................................................................ 26 

About this Master's Thesis

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School	Rollins School of Public Health
Department	Hubert Department of Global Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Epidemiology Health Sciences, Public Health
Stichwort	Covid vaccines
Committee Chair / Thesis Advisor	Castro, Kenneth, Emory University
Committee Members	Bednarczyk, Robert, Emory University

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