A high level of vaccine knowledge increases people's behavioral risks for contracting COVID-19 in Japan.

Background: There has been no study in which the association between levels of vaccine knowledge and preventive behaviors was examined during the COVID-19 pandemic. We examined the transition to risky (transmission) behavior according to level of vaccine knowledge over a seven-month period when vaccines became widely available in Japan.

Methods: A series of cross-sectional surveys were conducted using rapid online surveys of residents in Iwate Prefecture from December 4 to 7 in 2020 (the first survey) and from July 2 to 4 in 2021 (the fourth survey). We calculated each individual's risk of acquiring SARS-CoV-2 infection using a quantitative assessment tool (the microCOVID calculator). The respondents' level of knowledge regarding the COVID-19 vaccine was assessed by a questionnaire and was divided into four groups: very low level, low level, moderate level, and high level of vaccine knowledge.

Results: People with a high-level knowledge about the vaccine had significantly higher odds ratios (ORs) of transitioning to high-risk behavior compared to people with a low level of vaccine knowledge (OR [95% confidence interval (CI)], 1.50 [1.17-1.93]; P = 0.001). There was a dose-response association according to the four levels of vaccine knowledge, while engagement in preventive measures in the first survey was not associated with high-risk behavior in the follow-up survey.

Conclusions: Since new variants of SARS-CoV-2 have evolved, policy makers should continue to communicate strong messages to keep a high level of consciousness and maintain basic preventive measures even after widespread vaccination.