Pneumococcal vaccination coverage and vaccination-related factors among older adults in Japan: LIFE Study.

Purpose: To investigate individual and environmental vaccination-related factors among the older adults in Japan, using administrative data.

Methods: We conducted a cohort study and included people who reached the relevant age (≥65 years) for routine pneumococcal vaccination of older adults between April 2015 and March 2020. Monthly data of residents in the two municipalities from April 2014 to March 2020 and vaccination records from April 2015 to March 2020 were used. We defined five cohorts according to the year in which routine vaccinations were available. Each cohort was followed for a total of two years, with the first year being the "baseline period" and second year being the "vaccine follow-up period." Pneumococcal vaccination data was extracted from vaccination records at "first dose." Age, sex, socioeconomic status, comorbidities, hospital visit history, hospitalization history, Specific Health Check-ups participation, and information on contracted hospitals for pneumococcal vaccination were used as covariates. A multivariate logistic regression model was used to investigate the relationship between pneumococcal vaccination and vaccination-related factors. Odds ratios (OR) and 95 % confidence intervals (95 % CI) were calculated.

Results: Analysis included 17,991 patients. Vaccination coverage was 33.6 % for all subjects. Multivariate analysis found the following as significant vaccination-related factors: female (OR: 1.18, 95 % CI: 1.11-1.26), not low income (1.76, 1.17-2.76), hospital visits: ≥once/month (1.27, 1.19-1.35), and Specific Health Check-ups participation (2.10, 1.95-2.27). No significant results were found for hospitals that contracted pneumococcal vaccination.

Conclusions: Individual factors, such as sex and Specific Health Check-ups participation, were found to be important factors affecting pneumococcal vaccination among older adults in Japan. Environmental factors, such as the characteristics of residential areas, should be evaluated in further investigations.