Humoral immune responses of rAd5-PEDV-S in sows. (A) Schematic representation of the immunization procedure. These sows being immunized with a primary immunization at 5 weeks before farrowing and a secondary immunization with the same dose irradiated 2 weeks before farrowing and immunized only once each at 5 weeks before or 2 weeks before farrowing. (B) IgA antibody titers in colostrum. (C) IgG antibody titers in serum. (D) NAb titers in colostrum assay in Vero cells. (E) NAb titers in serum assay in Vero cells. (Data were analyzed by Tukey’s multiple comparison test for subsequent analysis. Each point represents the titer of an individual. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, no significance).