Figure 2.

Protective efficacy of the in-ovo NDV vaccine strain TS09-C in commercial chickens against challenge with different virulent NDVs. The in-ovo vaccinated commercial chickens were challenged with virulent NDV strain F48E9 at 28 dph (A, B) and virulent strain HB0901 at the indicated dph (C). (A) The NDV-specific hemagglutinin-inhibition (HI) antibody titers of immunized birds before challenge. (B) The survival percentages of challenged birds on different days after challenge. (C) The protection rates of chickens challenged at the indicated dph. The HI titers of chickens immediately before challenge are indicated at the top of each column. Statistical significances in survival between different groups were analyzed by Log Rank test (ns, P > 0.05; *, P < 0.05; **, P < 0.01).