Expanding the definition of invasive pneumococcal disease in children aged 3-42 months to include suspected cases and unspecified sepsis significantly improved the cost-effectiveness of the 10-valent pneumococcal conjugate vaccine, Dr. Arto A. Palmu and his associates reported.

In a nationwide observational follow-up study, Dr. Palmu and his associates found that the relative rate reduction for non–laboratory-confirmed invasive pneumococcal disease (IPD) and unspecified sepsis was only 34%, compared with 80% for culture-confirmed IPD. The absolute rate reduction was much higher. For culture-confirmed IPD, the absolute rate reduction was 50 cases per 100,000 person-years, and for non–laboratory-confirmed IPD and unspecified sepsis, the rate was 122 cases per 100,000 person-years, said Dr. Palmu of the National Institute for Health and Welfare in Tampere, Finland.

Mortality reduction was 51% overall. For non–culture-confirmed IPD and unspecified sepsis, the relative mortality reduction was 35%.

“Use of sensitive case definitions, such as clinically suspected IPD, in the evaluation of the total disease burden prevented by the vaccination program is important for understanding the total burden of pneumococcal disease and the cost-effectiveness of public health interventions,” the investigators concluded.

Find the full study in Pediatrics (doi:10.1542/peds.2015-0458).