Table 2.

Serosurveillance of influenza A virus exposure in the Norwegian pig population between 2009 and 2017

HAIT titre threshold for positivity	Number of pigs sera HAIT positive for H1N1pdm09 (% change in sensitivity)	Number of pigs sera with heterologous reactions (reduction in %)
>10 (ref)	8,393	6, 259
≥20	8,200 (−2%)	5,183 (−17.1%)
≥40	8,200 (−2%)	5,175 (−17.3%)

Comparing sensitivities of the HAIT in detecting immunogen H1N1pdm09 and amount of heterologous reactions at different HAIT titre thresholds (a) >10, (b) ≥20 and (c) ≥40.