Pneumonia hospitalization after introduction of pneumococcal conjugate vaccine in Japan: Descriptive study using a nationwide claims database

Abstract

BackgroundThe pneumococcal conjugate vaccine (PCV) was introduced to children in Japan in February 2010 for PCV7 and February 2013 for PCV13. This study aimed to investigate the changes in child pneumonia hospitalization in Japan, before and after the introduction of PCV. MethodsWe utilized the JMDC Claims Database, an insurance claims database in Japan, with a cumulative population of approximately 10.6 million as of 2022. We extracted data of approximately 3.16 million children below 15 years of age from January 2006 to December 2019, and evaluated the number of pneumonia hospitalizations per 1,000 persons per year. The primary analysis was a comparison of three categories according to PCVs: before PCV7, before PCV13, and after PCV13 (2006–2009, 2010–2012, and 2013–2019). The secondary analysis was an interrupted time series (ITS) analysis, assessing the slope change in pneumonia hospitalizations per month, with PCV introduction as an intervening factor. ResultsThe cases of pneumonia hospitalizations during the study period was 19,920 (0.6 %); 25 % of these were 0–1 years, 48 % were 2–4 years, 18 % were 5–9 years, and 9 % were 10–14 years. Pneumonia hospitalizations per 1000 population was 6.10 before PCV7 and 4.03 after PCV13, representing a 34 % decrease (p < 0.001). The reduction by age group was –30.1 % in 0–1 years, –20.3 % in 2–4 years, –41.7 % in 5–9 years, and –52.9 % in 10–14 years, significant reduction in all groups. ITS analysis showed a further reduction of –0.17 % per month after the introduction of PCV13 than that before PCV7 (p = 0.006). ConclusionOur study estimated 4–6 pneumonia hospitalizations per 1000 pediatric population in Japan, with a 34 % decrease after the introduction of PCV. This study examined the nationwide effectiveness of PCV, further studies are needed in all age groups.