Abstract
BACKGROUND: The Japanese vaccination rate for infants and children is seemingly excellent, except for the human papillomavirus (HPV) vaccine. Regardless of its efficacy, the inoculation rate in Japan has dropped to approximately 1 % since 2013 because of negative information about vaccine side effects. We aimed to demonstrate the factors that lead to low vaccine acceptance rates (e.g., caregiver attitudes, popular misconceptions) to inform the relevant target demographic of a stronger intention to immunize and to facilitate recovery of HPV vaccine coverage. METHODS: We conducted this study using data from two questionnaire surveys. Statistical analyses of factors affecting vaccine impressions and mediation effects of HPV vaccine impressions were performed. The difference in the knowledge about each vaccine was evaluated. RESULTS: Of the respondents, 95.9 % reported their intent to vaccinate their infants, whereas 58.2-78.3 % felt that they sufficiently understood the aims, efficacy, and risks of vaccination and 66.6 % had a positive impression of vaccines. Overall, 21.3 % of parents responded that they planned to have their child vaccinated against HPV, and 25.8 % had a favorable impression of this vaccine. Among factors affecting vaccine impressions, we found that parents had anxiety about vaccines when they felt that their knowledge of vaccines was insufficient. Additionally, impressions of the HPV vaccine had a mediating effect on the association between the impressions of infant vaccines and parents' intent to provide the vaccine to their children. CONCLUSION: These findings show that as a society, we need to improve impressions and knowledge regarding vaccines, including but not exclusively the HPV vaccine. Moreover, although the recovery of HPV vaccine coverage is strongly desired for improving public health, simply improving impressions about the HPV vaccine or educating parents with substantive knowledge is insufficient. Instead, improving impressions and understanding of the vaccination itself is necessary.