Fig. 4. Influenza A virus-specific serologic immune responses.

Measurements were achieved by A a nucleoprotein-specific indirect ELISA (ID-VET NP) and B by a hemagglutination inhibition assay using the swIAV H1pdmN2 isolate AI03362 as antigen. A - S/P value >0.4 is regarded as positive (dashed line), B – Titers of 3 log2 (1:20) are considered specifically positive. Error bars indicate the standard deviation of the median. d0 – Serum sample obtained at day 28 of age before vaccination at day 35; 20, 27 dpv - 3 weeks after first and 1 week after booster vaccination; 4, 7, 14 dpc – days post contact challenge (1 week after the booster vaccination). Dashed line – A threshold of S/P value = 0.4, B threshold of 1:20 (log₂ 4,3).