Titers of anti-hMPV and anti-hRSV IgG antibodies. Twenty human serum samples that were seropositive for hMPV (A) or hRSV (B) were randomly selected from each age group, for a total of 160 samples. ELISA was performed using hMPV N protein or hRSV N protein as the antigen. Titers are shown for the indicated age groups. Horizontal bars indicate the GMTs of antibodies against hMPV or hRSV.