Number of hospitalizations for aspiration pneumonia (upper panel) and CAP (lower panel) per month across the 47 study hospitals. Number of hospitalizations for aspiration pneumonia (upper panel) and CAP (lower panel) per month across the 47 study hospitals. Although seasonal variation was observed among hospitalizations for both CAP (IRR = 1.38, 95% CI 1.36–1.39) and aspiration pneumonia (IRR 1.16, 95% CI 1.12–1.21), the magnitude of the seasonal effect was significantly larger for CAP relative to aspiration pneumonia (χ2 for interseasonal δ between groups, P < .001). Alexander W. Hirsch et al. Hospital Pediatrics 2016;6:659-666 ©2016 by American Academy of Pediatrics