Researchers at University of Tsukuba have demonstrated that during Japan’s COVID-19 booster vaccination campaign, online information influenced vaccination intentions in ways similar to the initial rollout. The study identified a “cyclical effect,” whereby an increase in vaccination intent prompted further information-seeking behavior, which in turn reinforced beliefs and attitudes.
Japan’s COVID-19 vaccination program began in 2021 with a two-dose primary series that rapidly achieved widespread coverage. As new variants emerged, booster doses were recommended. However, the type of information that would influence previously vaccinated individuals to form vaccination intentions regarding booster shots remained unclear.
This study, published in Vaccine, surveyed 594 Japanese adults aged 25–64 through an online research company at two time points: February 2022, when booster shots became available to the general adult population under 65 and four months later.
The researchers examined the relationship between online information and vaccination intent. Drawing on prior research, online vaccine-related information was classified into three types: (1) information on vaccine efficacy and side effects, (2) practical information regarding when and where the boosters could be obtained, and (3) domestic and international vaccination trends.
The findings revealed that practical information about vaccine availability enhanced self-efficacy and perceived benefits, strengthening vaccination intent. Conversely, technical information on vaccine efficacy and side effects reduced perceived benefits and weakened intent. Notably, the study confirmed a cyclical effect: stronger vaccination intent led to increased information-seeking behavior, which further reinforced beliefs and attitudes. These patterns were aligned with those observed during the initial rollout.
This study provides empirical evidence that, post-vaccine dissemination, a dynamic interplay persists between online information and vaccination intent where they mutually reinforce one another. These insights are essential for the design of effective information strategies during future outbreaks of infectious diseases.
More information:
Sanae Inoue et al, The mutual cyclical influence of internet information and vaccination intention on post-dissemination vaccination: A longitudinal study during the availability period of COVID-19 booster shots, Vaccine (2025). DOI: 10.1016/j.vaccine.2025.127741
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