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Purpose: In Japan, both a 23-valent pneumococcal polysaccharide vaccine (PPSV23) and a 13-valent pneumococcal conjugate vaccine (PCV13) are available. Although randomized controlled trials have examined the effects of pneumococcal vaccines, few epidemiological studies have investigated the onset of pneumococcal pneumonia in general practice. In Izumo, Shimane Prefecture, Japan, a public subsidy for PPSV23 inoculation began in November 2012. Patients and Methods: The subjects were pneumonia patients aged 65 and over who were admitted to a hospital in Izumo. This retrospective study analyzed the following data extracted from medical records: pneumococcal pneumonia prevalence, pneumonia severity, mortality rate, PPSV23 vaccination rate, and length of hospital stay. The 2 years before the start of the public subsidy were defined as the early phase, and the 2 years after the subsidy initiation were defined as the late phase. We compared the two phases in terms of PPSV23 vaccination rate, prevalence and severity of pneumococcal pneumonia, and mortality rate. Results: We investigated data from a total of 1188 and 1086 patients in the early and late phases, respectively. The prevalence of pneumococcal pneumonia was 21.0% and 21.3% in the early and late phases, respectively. The mortality rate from pneumococcal pneumonia was 10.4% and 5.4% in the early and late phases, respectively (p = 0.080), indicating a 50% reduction. The PPSV23 vaccination rate (p < 0.001) and the comorbidity rates of chronic respiratory disease (p = 0.022) and chronic renal disease (p < 0.001) were significantly different between the early and late phases. Conclusion: This study showed that the rate of in-hospital deaths due to pneumococcal pneumonia was halved after the PPSV23 vaccine was subsidized. The causal relationship between the pneumococcal vaccination rate and the mortality rate of pneumococcal disease was unclear. Further investigation is deemed necessary. [ABSTRACT FROM AUTHOR]

The decline in the proportion of pneumococcal conjugate vaccine (PCV)-covered serotypes among adult invasive pneumococcal disease (IPD) patients might change the overall effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) because its effectiveness differs according to serotype. Using the indirect cohort method, we calculated the effectiveness of PPSV23 against IPD among adults in Japan to assess the impact of the national pediatric PCV program. Clinical and epidemiologic information and pneumococcal isolates were collected from IPD patients >20 years of age through enhanced IPD surveillance during April 2013-December 2017. Adjusted effectiveness against PPSV23-serotype IPD was 42.2%. Despite a substantial decline in the proportion of 13-valent PCV serotypes during the study period (45% to 31%), the change in effectiveness for PPSV23-serotype IPD was limited (47.1% to 39.3%) and only marginal in the elderly population (39.9% to 39.4%). The pediatric PCV program had limited impact on PPSV23 effectiveness against IPD in adults.

After 7-valent pneumococcal conjugate vaccine (PCV) for children was introduced in Japan in November 2010, we examined changes in Streptococcus pneumoniae serotypes and in genetic antimicrobial drug resistance of isolates from adults with invasive pneumococcal diseases. During April 2010-March 2013, a total of 715 isolates were collected from adults with invasive pneumococcal diseases. Seven-valent PCV serotypes in adults decreased from 43.3% to 23.8%, most noticeably for serotype 6B. Concomitantly, 23-valent pneumococcal polysaccharide vaccine (PPSV23) serotypes decreased from 82.2% to 72.2%; non-PPSV23 serotypes increased from 13.8% to 25.1%. Parallel with serotype changes, genotypic penicillin-resistant S. pneumoniae decreased from 32.4% to 21.1%, and 6 non-PPSV23 serotypes emerged (6D, 15A, 15C, 16F, 23A, and 35B). Respective vaccine coverage rates for 13-valent PCV and PPSV23 differed by disease: 73.9% and 84.3% for patients with pneumonia, 56.4% and 69.2% for patients with bacteremia and sepsis, and 45.7% and 69.3% for patients with meningitis.