Purpose The lack of evidence on the disease burden has been an obstacle for decision-making on introducing pneumococcal vaccines in Sri-Lanka. Hence, the purpose of this study is to determine the incidence of invasive pneumococcal disease among children under five-years of age in Sri-Lanka's Colombo district.

Methods In a community-based study, using a sample of 2310 children, we identified syndromes associated with pneumococcal disease (pneumonia, meningitis, sepsis). The estimates of annual cumulative incidence of invasive pneumococcal disease were derived by having applied proportions of laboratory confirmed invasive pneumococcal disease among all-cause syndromes associated with pneumococcal infection obtained from the hospital-based invasive bacterial disease sentinel surveillance and findings of the community-based study to population parameters of the district. The estimates of invasive pneumococcal pneumonia and sepsis based on low-sensitive, culture confirmation were adjusted by a correction factor.

Results The annual cumulative incidence of all-cause clinical syndromes associated with pneumococcal disease (pneumonia, meningitis, sepsis) were 1.3, 0.52, 0.39 per 100 children, respectively. The estimate of adjusted, invasive pneumococcal disease cumulative incidence was 206.3 per 100,000 while estimates of pneumococcal pneumonia, meningitis and sepsis cumulative incidence were 147.9, 13.2 and 45.2 per 100,000 under-five children.

Conclusion Reasonable estimates of invasive pneumococcal disease could be derived by using incidence of clinical syndromes associated with pneumococcal disease obtained from population-based studies and proportion of pneumococcal infection among all-cause clinical syndromes associated with pneumococcal disease generated from hospital-based sentinel surveillance. These estimates may help informed decision-making on introduction of pneumococcal conjugated vaccine.