16 17 A retrospective analysis of three healthcare claims repositories in the USA showed that PP and IPD rates were approximately three times higher in immunocompetent adults with one or more chronic conditions (‘at-risk’ adults) compared with age-matched healthy adults. Several studies have been conducted in the USA and Germany to examine the burden of pneumococcal disease in persons with underlying medical conditions.
Since 2007, 14 15 the Japanese Respiratory Society has advocated an expansion of the programme to individuals aged 2–64 years with chronic or immunosuppressive conditions. 9–12 Since 2014, 13 the National Immunisation Programme in Japan has implemented the use of PPV23 for adults aged 60–64 years with underlying medical conditions, in addition to adults aged ≥65 years. The 23-valent pneumococcal polysaccharide vaccine (PPV23) was licensed in 1988 in Japan, and studies have revealed the protective effects of PPV23 against invasive pneumococcal disease (IPD) and pneumococcal pneumonia (PP). 3 4 These high-risk groups have been targeted for pneumococcal vaccination to reduce the burden of pneumococcal disease in many countries, including the USA, Canada, the UK and Germany. 1 2 In addition, adults with certain chronic medical conditions, such as diabetes, chronic lung disease and chronic heart disease, are also at increased risk of pneumococcal disease. Older adults and children, as well as immunosuppressed individuals, such as those with HIV, are susceptible to pneumococcal disease. Pneumococcal disease, caused by encapsulated Streptococcus pneumoniae, is a major cause of community-acquired pneumonia, meningitis, septicaemia, osteomyelitis, septic arthritis and bacteraemia worldwide. Results from only one database cannot be extrapolated to the general population of adults in Japan, and subjects in the two databases may be representative of different adult populations.
These analyses did not consider potential confounders other than age and sex, such as pneumococcal vaccination history and residential environment, which might significantly influence the risk of pneumococcal pneumonia and invasive pneumococcal disease. Our study results may contribute to further knowledge on the risk of pneumococcal disease in Japanese individuals aged ≥19 years with an underlying medical condition.Īs this study was a retrospective analysis based on insurance claims data, the coding of medical conditions and episodes of pneumococcal pneumonia and invasive pneumococcal disease by the International Statistical Classification of Diseases and Related Health Problems version 10 codes may lead to misclassification, and pneumococcal pneumonia may be undercoded. Given the well-known differences in the genetic makeup of the Japanese population, data specific to Japan are important to formulate a national immunisation strategy and to protect vulnerable populations.
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