Event-Driven Vaccine Hesitancy During Pandemic: A Comparative Analysis of Demographic and Cultural Influences

Abstract

COVID-19 has posed an unprecedented global public health challenge, leading to widespread infections, high mortality, and profound social and economic disruptions worldwide. Vaccine hesitancy remains a critical barrier to effective pandemic control, arising from a complex interplay of factors, among which vaccine-related events—including policy interventions, information dissemination, and negative vaccine news—play a pivotal role in shaping public risk perceptions and vaccination willingness over time. While previous studies have investigated determinants of vaccine hesitancy across countries, most have adopted static or cross-sectional perspectives, overlooking the temporal dynamics induced by unpredictable vaccine-related events—occurrences that reflect multifactorial influences and cannot be meaningfully reduced to isolated drivers.

This study addressed this gap by proposing a social-epidemiological transmission model integrated with the game-theoretic imitation mechanism and payoff-driven risk perception framework. Focusing on event-driven vaccine hesitancy, we investigated the interplay between COVID-19 transmission dynamics, vaccination behaviors, and external vaccine-related events through three interconnected analyses. We used Hong Kong as a baseline case and extended it to age-stratified subgroups and cross-country comparisons with France.

First, considering Hong Kong's contact-tracing policies, we extended the classical SEPIRD model by incorporating a contact-tracing module and time-varying vaccination rates modulated by risk perception dynamics. Vaccine uptake was quantified through a composite payoff function that synergistically integrates two components: (1) infection and mortality risk reduction post-vaccination; and (2) vaccine-related events, including negative news and incentive measures. Our analysis reveals that the negative news drastically impeded vaccination efforts. However, we found that vaccination willingness declined rapidly after the incentive measures were discontinued, implying limited benefits in mitigating the effect of negative news in the long run. This study also highlights the need for booster doses in the face of the immune escape of the Omicron variants.

Second, we stratified Hong Kong's population into four age groups (0–19, 20–49, 50–69, and ≥70 years) to analyze age-specific sensitivities to vaccine hesitancy drivers. Fitting the model to real-world infection and vaccination data, we identified distinct age-related patterns: (1) the 50–69 age group exhibited a sensitivity to adverse event reports comparable to the 20–49 age group, but their reponse to reduced information regarding deaths potentially associated with vaccination more closely resembeled that of the ≥70 age group; (2) all age groups except the 0–19 age group showed substantially improved vaccination willingness, and the ≥50 age group showed greater payoff gains; (3)booster campaigns universally enhanced primary vaccination rates, particularly in the 20–69 age groups.

Third, extending the framework to France, we simplified the model by removing contact tracing components to explore cultural and policy-specific drivers. Key findings include: (1) safety-related events (e.g., reports of trial shortcomings or side effects) universally reduced vaccine willingness; (2) anti-vaccination protests (e.g., “freedom rallies” opposing “health dictatorships”) severely disrupted vaccination progress, highlighting the politicization of public health measures in specific cultural contexts.

Date of Award	2 Oct 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Linyan LI (Supervisor), Qingpeng ZHANG (Co-supervisor) & Hsiang-Yu Sean YUAN (Co-supervisor)