OBJECTIVES:

Streptococcus pneumoniae infections can lead to severe diseases such as bronchitis, pneumonia, and sepsis. Japan has established routine pneumococcal vaccinations for children aged ≤5 years and older persons aged ≥65 years due to their higher risk of infection. However, exploring the risk factors for pneumococcal disease may identify other at-risk populations for inclusion in vaccination programs. This study aimed to identify the risk factors for pneumococcal disease in a Japanese population.

METHODS:

The study was performed using insurance claims data from the residents of 12 Japanese municipalities. Based on recorded diagnoses, we identified chronic medical conditions in each subject between April 2015 and March 2016, and examined the subsequent occurrence of pneumococcal disease from April 2016 onward. Cox proportional hazards models were used to estimate the hazard ratio of each chronic medical condition for pneumococcal disease occurrence.

RESULTS:

The study was conducted on 732,235 subjects, of which 61,306 (8.4%) were aged 0-18 years, 184,367 (25.2%) were aged 19-49 years, 126,078 (17.2%) were aged 50-64 years, and 360,484 (49.2%) were aged ≥65 years. The total observation period spanned 2,724,028 person-years, during which 1,466 cases of pneumococcal disease occurred. The overall incidence rate was 53.8 per 100,000 person-years. A higher number of conditions was associated with a higher incidence of pneumococcal disease. Significant risk factors for pneumococcal disease in all subjects included chronic heart disease, chronic lung disease, diabetes, cancer, and chronic renal disease. Furthermore, chronic lung disease, diabetes, aspiration pneumonia, and immunosuppressant use were risk factors among subjects aged 50-64 years.

CONCLUSIONS:

Persons aged 50-64 years with multiple chronic medical conditions or with specific conditions are at higher risk of developing pneumococcal disease, indicating a need to consider their inclusion in routine vaccination programs.