Figure 1

Graphical representation of how person-time at risk of being hospitalized for bronchiolitis was calculated for non-prophylaxed and prophylaxed infants. For prophylaxed infants, two different approaches were proposed. Box A shows that person time was calculated since the first date of Palivizumab administration to the first hospitalization for bronchiolitis, or the date the subject turned 18 months of age, or the first of January 2007, whichever comes first. Box B shows that, compared to the previous approach, the person-time does not include the time-periods exceeding the 30 days after each Palivizumab administration. In this case also hospitalizations for bronchiolitis happened in the dashed periods are not considered.