Protective efficacy of vaccine viruses Ban/AF and B1 in 1-day-old chicks against challenge with virulent strains

<p><b>Ban/010 and GB Texas.</b> Chicks were inoculated with vaccine viruses Ban/AF or B1 by a single nasal drop each, or were mock-infected, as described in Materials and Methods. At 21 dpi, birds from each group were challenged with 100 LD50 of the Ban/010 or GB Texas viruses by the oculonasal route. The birds were observed daily for survival. Each challenge group had 10 birds except for the 1-day-old chicks immunized with Ban/AF, which had 12 birds in the Ban/010 challenge group and 11 birds in the GB Texas challenge group.