Three of 94 hospitalized children (3%), two with underlying diseases, had been vaccinated against PIA five days (n = 2) or about two months before hospitalization (n = 1). One child without underlying diseases had been vaccinated against seasonal influenza before hospitalization (no information about date of vaccination). Only two (5%) of 40 children with underlying chronic conditions for whom influenza vaccination is generally recommended in Germany had received PIA vaccination, compared to one child (2%) of the 54 children without underlying chronic conditions. None of the six children with severe complications had received any influenza vaccination.