A steady-state, population-based model to estimate the direct and indirect effects of pneumococcal vaccines
This paper estimated the clinical impact of routine vaccination of infants with a new 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) compared with the 7-valent pneumococcal conjugate vaccine (PCV-7) and no vaccination in Canada using a new steady-state, population-based model. A deterministic, compartmental model was developed to simulate the effect of vaccination for a 1-year time period for a steady-state population, allowing for the incorporation of herd and replacement effects across all age groups. Annual clinical outcomes in the steady-state year for a population of 32.9 million were calculated for all three vaccination strategies. The no vaccination strategy was included for the purpose of validating the model. The model estimated that PHiD-CV prevented more cases of disease and more deaths than PCV-7 and no vaccination, with the largest incremental impact on acute otitis media (AOM). Compared with PCV-7, vaccination with PHiD-CV was estimated to prevent an additional 10 cases of invasive disease, 416 cases of pneumonia, 155,757 cases of AOM, 8943 myringotomy procedures, and 6 deaths nationwide. For the comparison between PCV-7 and no vaccination, the model estimated a 36.8% reduction in invasive disease; this result was similar to other models and a recent observational study in Canada, providing preliminary validation of the model.