Risk of pneumococcal diseases in adults with underlying medical conditions: a retrospective, cohort study using two Japanese healthcare databases

OBJECTIVES: To quantify the risk of pneumococcal pneumonia (PP) and invasive pneumococcal disease (IPD) in adults aged ≥19 years with underlying medical conditions compared with healthy adults of the same age in Japan. DESIGN: An observational, retrospective, cohort study using two healthcare claims databases in Japan: Japan Medical Data Center (JMDC) and Medical Data Vision (MDV) databases. PARTICIPANTS: A total of 10.4 million individuals, representing 9.3 million person-years of follow-up, were included in the analysis. Eleven medical conditions as well as PP and IPD were identified by the International Statistical Classification of Diseases and Related Health Problems version 10 diagnostic codes and/or local disease codes used in Japan. PRIMARY OUTCOME MEASURES: Adjusted rate ratios (RRs) for PP and IPD in adults with a medical condition versus adults without any medical condition were calculated using multivariate Poisson regression models with age and/or sex as covariates. RESULTS: In the JMDC and MDV databases, respectively, adults ≥19 years with a medical condition (RRs for PP: 3.3 to 13.4, 1.7 to 5.2; RRs for IPD: 12.6 to 43.3, 4.4 to 7.1), adults with two or more medical conditions (PP: 11.6, 2.8; IPD: 18.7, 5.8) and high-risk adults (PP: 12.9, 1.8; IPD: 29.7, 4.0) were at greater risk of PP and IPD compared with their healthy counterparts. Adults aged 50–64 years with an underlying medical condition (PP rate: 38.6 to 212.1 per 100 000 person-years) had a higher rate of PP than those aged ≥65 years without any condition (PP rate: 13.2 to 93.0 per 100 000 person-years). CONCLUSIONS: Adults of all ages with an underlying medical condition are at greater risk of PP and IPD compared with adults without any medical condition. This risk increases with the number of underlying medical conditions. Our results support extending pneumococcal vaccination to younger adults with an underlying medical condition, especially those aged 50–64 years.