Acceptance of Booster COVID-19 Vaccine and Its Association with Components of Vaccination Readiness in the General Population: A Cross-Sectional Survey for Starting Booster Dose in Japan

The Japanese government approved COVID-19 vaccine booster doses in November 2021. However, intentions and readiness for booster vaccines among the general population were unknown. This survey measured the intentions for COVID-19 booster vaccination. Among 6172 participants (53.2% female), 4832 (78.3%) accepted booster doses; 415 (6.7%) hesitated. Vaccination intention was associated with higher age, marital status, having children, underlying diseases, and social norms. To evaluate the readiness for vaccination, the seven component (7C) vaccination readiness scale was employed, comprising "Confidence", "Complacency", "Constraints", "Calculation", "Collective responsibility", "Compliance", and "Conspiracy". Participants with acceptance showed significantly higher 7C scores (p < 0.001) than those who hesitated or were unsure. Multivariable logistic regression analysis revealed that the "social norms" predictor was the strongest predictor of acceptance (adjusted odds ratio (AOR) 4.02, 95% confidence interval (CI): 3.64-4.45). "Constraints" (AOR: 2.27, 95% CI: 2.11-2.45) and "complacency" (AOR: 2.18, 95% CI: 2.03-2.34) were also strongly associated with acceptance, but "compliance" (AOR: 1.24, 95% CI: 1.18-1.31) and "conspiracy" (AOR: 1.42, 95% CI: 1.33-1.52) were weakly associated. The "7C vaccination readiness scale" is useful for measuring vaccine acceptance in the Japanese population. However, "social norms" might be more suitable than "compliance" and "conspiracy" for measuring vaccine acceptance in Japan.