Figure 1.

Kinetics of the IgG antibody levels against the NP detected by ELISA in sera after vaccination and viral challenge. IgG antibodies measured as percentage of competition at first vaccination (0 dpv), 21, 42 dpv (day of challenge) and at 2, 5, and 10 dpi are depicted. Points above the dashed red line (competition > 45%) are considered positive, whereas points under the dashed grey line (competition < 50%) are considered negative. Values between the two lines are considered doubtful. Groups of vaccinated and nonvaccinated animals are shown in blue and green, respectively.