IFNA1 and infection: In this study, responses after the initial H1N1 challenge were comparable in each group H1/H3, H1/H1 and H1/cull with IFN-ɣ detectable by 8 days post-infection and the peak H1N1-specific IFN-ɣ production at 11 days post-infection, followed by a fall in response up to day 26 post-infection (Fig. 8a).