Safety and efficacy studies on trivalent inactivated vaccines against infectious coryza

The safety and efficacy of an inactivated oil-emulsion infectious coryza vaccine containing three Avibacterium paragallinarum isolates (one each of Page serovars A, B, and C) was evaluated. The safety of six batches of the vaccine was confirmed by testing with chickens vaccinated with a single large dose or vaccinated repeatedly with a normal dose. Efficacy tests were carried out on three batches of vaccine using both specific pathogen free (SPF) chickens and conventional chickens. In SPF chickens given a single vaccination at 42 days of age, the protection rate against all three serovars of Av. paragallinarum was at least 80% at 30 days post vaccination. The conventional chickens, which were immunized at 42 and 110 days of age, were challenged at 9 months post the second vaccination and the protection rate was at least 80% for all three serovars. The effect of storage on the vaccine was evaluated in SPF chickens using three batches of vaccine stored at 4–8 °C for 1 year. The protection rate against challenge from all three serovars (single vaccination at 42 days of age and challenge at 30 days post-vaccination) was at least 80%.