Seasonality of Both Bacteremic and Nonbacteremic Pneumonia Coincides With Viral Lower Respiratory Tract Infections in Early Childhood, in Contrast to Nonpneumonia Invasive Pneumococcal Disease, in the Pre-Pneumococcal Conjugate Vaccine Era

We assessed the seasonality of viral lower respiratory tract infections (V-LRI), bacteremic pneumonia, nonbacteremic pneumonia and nonpneumonia invasive pneumococcal diseases (IPD) in the pre-PCV era. Both bacteremic and nonbacteremic pneumonia seasonality peaked in winter, coinciding with V-LRI seasonality, whereas non-pneumonia IPD peaked in autumn before V-LRI increase, suggesting different pathogenesis.