Table 2.

Influence of pre‐existing H3N8 antibody levels on booster vaccination response

Pre‐existing antibody levels at time of vaccination	Number of animals responding by SRH (%)	Number of animals responding by ELISA (%)
Negligible	3/3 (100)	3/3 (100)
Low	6/6 (100)	5/6 (83)
Medium	13/15 (87)	7/9 (78)
High	3/14 (21)	1/20 (5)
Total	25/38 (66)	16/38 (42)

For SRH antibody level Negligible ≤ 50 mm²; Low ≥ 50 mm² < 85 mm²; Medium ≥ 85 mm² < 150 mm²; High ≥ 150 mm².

For ELISA competition percentage Negligible ≥ 85%; Low ≥ 50% < 85%; Medium  ≥ 15% < 50%; High ≤ 15%.