Effect of influenza vaccine subsidies for older adults on vaccination coverage and mortality before and during the COVID-19 pandemic: an ecological study in Japan

Abstract

Objective: We aimed to determine how municipal subsidies for seasonal influenza vaccines for the elderly affected vaccination coverage and health outcomes and how responses to vaccine prices changed during the COVID-19 pandemic.

Study design and methods: This ecological study includes 1245 municipalities in Japan between 2019 and 2020. Fixed-effects regression analysis was performed to evaluate the effect of influenza vaccine cost subsidy for people aged 65 years or older on vaccination coverage, all-cause mortality, and influenza-related mortality.

Results: The vaccination rate increased when patients' copayments decreased, and reducing the copayment by 1000 Japanese Yen (JPY) was estimated to increase the vaccination rate by 6.3% (95% confidence interval [CI] 4.5-8.2%) in the adjusted model. When examining the additional effect of a zero price compared to a nearly zero price, we found that a zero price increased the immunization rate by 6.4% (95% CI 1.4-11.5%). The effect of copayment on the increase in vaccination coverage was significantly lower during the pandemic than in the pre-pandemic period. The municipal and prefectural analyses found no association between influenza vaccine copayments and all-cause, influenza, or pneumonia mortality.

Conclusion: Cost subsidies and the zero-price effect were shown to increase vaccination coverage but were not associated with relevant mortality measures. Although the impact was attenuated under pandemic conditions, cost subsidy effectively increases the vaccination rate.

Keywords: COVID-19; Influenza vaccine; Mortality; Subsidy; Zero-price effect.