Figure B1.

Propensity score distribution for children exposed and unexposed to palivizumab. Propensity scores range from 0 to 1 with 1 being the greatest probability for palivizumab use. The distribution shows good overlap allowing for balanced comparisons of exposed versus unexposed subjects, except at high scores (>0.8). Because exposed and unexposed groups showed only limited overlap in both tails of the propensity score distribution, we performed a sensitivity analysis by excluding patient seasons in the lower (PS < 0.08) and upper (PS > 0.8) tails. Event numbers dropped to 23 RSV‐related hospitalizations and 110 ARI‐related hospitalizations in a total of 2,037 patient seasons after trimming. Current exposure to palivizumab showed an HR of 0.57 (95% CI: 0.20–1.63) in the updated model for RSV‐related hospitalizations and 0.78 (95% CI: 0.48–1.25) in the updated model for ARI‐related hospitalizations.