Effects of the 23-Valent Pneumococcal Polysaccharide Vaccine on the Mortality of Pneumonia among Elderly over 70 Years Old after the Great East Japan Earthquake—PPV Vaccination Program in Iwate Prefecture, Japan

Abstract

Objective: To estimate the efficacy of 23-valent pneumococcal polysaccharide vaccine (PPSV23) among the elderly, we analyzed the relationship between the mortality of the elderly for pneumonia and the vaccination rate of PPSV23 from 2008 to 2016 in Iwate Prefecture, Japan. Study Design: The present study was a retrospective, observational, database study adopting an ecological design. The mortality for pneumonia among the elderly over 70 years old from 2006 to 2016 in Iwate Prefecture was calculated based on the data from the Japanese Vital Statistics. We compared the mortality rate (MR) of pneumonia among the elderly over 70 years old between the low-vaccinated period (LVP) (2006-2010) and high-vaccinated period (HVP) (2012-2016) using a Poisson regression model. Results: While the vaccination rate of PPSV23 among the elderly over 65 years old was 3.3% in 2010, it increased rapidly up to 40.7% in 2012 and reached 66.4% in 2016. The MR ratio of the total population during HVP to the average MR during LVP was 0.749. The MR of the total population during HVP was significantly lower than that during LVP (p < 0.001). Notably, the MRs of both men and women during HVP were significantly lower than those during LVP (p < 0.001). The significant decrease in MR during HVP started in 2012 and continued up to 2016. Conclusion: The increase in vaccination rate of PPSV23 during HVP (2012-2016) may contribute to the decrease in mortality for pneumonia among the elderly over 70 years old in Iwate Prefecture.