IgY titers to ER in serum. A IgY-titers to the ER challenge strain in serum from uninfected chickens or chickens experimentally infected with ER on day 0, “naïve” and “vaccinated” groups. Sera were collected at the indicated days from uninfected chickens, naïve chickens and vaccinated chickens. B IgY-titers to the ER challenge strain (Challenge) and the ER “vaccine related” strain (Vaccine), respectively, in sera collected on days −3 and 15, respectively, from uninfected chickens, naïve chickens and vaccinated chickens. A and B Results are shown as group mean values ± 95% CI where non-overlapping CI indicate statistically significant differences. On days −13, −3 and 15 n = 13/group, on days 1, 5 and 8 n = 7/group and on days 3 and 11 n = 6/group. C–E IgY-titers to the ER challenge strain (x-axis) and to the ER “vaccine related” strain (y-axis) for individual uninfected chickens (C) and “naïve” chickens (D) and “vaccinated” chickens (E) infected with ER on day 0. Sera were collected on day –3 and on day 15. Trend lines were calculated for each group and sample collection day using the curve fit power mode in the software KaleidaGraph, version 4.1.0 (Synergy Software) and equations and R-values are shown in each panel. For details see “Materials and methods” section.