IFNG and influenza: After 12 months, 56 (31 girls/25 boys) of the 70 children had been re-infected or infected with a new strain of influenza A/H1N1, A/H3N2, and/or B, as indicated by at least a four-fold increase in the HI antibody titer and/or a two-fold increase in IFNγ-positive SFU (Figure 1A,B and Figure 2B).