Estimating the burden of hospitalization for pneumococcal pneumonia in a general population aged 50 years or older and implications for vaccination strategies.

Streptococcus pneumoniae is a major cause of human infectious diseases worldwide. Despite this documented evidence, data on pneumococcal disease rates among general populations are scant because of the frequent lack of cultural identification. In this study we propose a model for estimating the burden of pneumococcal pneumonia on hospitalizations. The study was performed by analyzing administrative and clinical data of patients aged 50 years or older, resident in Sicily, and hospitalized, from 2005 to 2012. Demographic information, admission/discharge dates, discharge status, and up to 6 discharge diagnoses coded according to ICD-9 CM were collected for each hospitalized patient. During the 8-year study period, a total of 72 372 hospitalizations with at least one ICD-9 CM diagnosis code suggestive of all-cause pneumonia were recorded. Of these, 1943 (2.7%) hospitalizations had specific ICD-9 CM diagnosis codes for pneumococcal pneumonia. According to the proposed model, 16 541 (22.9%) pneumonia out of all-cause pneumonia was estimated to be attributable to S. pneumoniae. Pneumococcal pneumonia and model-estimated pneumococcal pneumonia had mean hospitalization rates of 13.4 and 113.3/100 000, respectively, with a decreasing temporal trend. The risk of hospitalization for pneumococcal pneumonia was strongly correlated with age (P < 0.001). Our model provides data usable to construct suitable decisional models for the decision-makers and could allow to the responsibles of healthcare facilities to assess the budget impact if they hypothesize to offer vaccination for pneumococcal disease to certain cohorts of subjects aged 50 years or older. In our area, the high estimated hospitalization rates among adults aged ≥65 years suggest the need to implement effective preventive strategies (e.g., vaccination) tailored for these groups.