An evaluation of inactivated infectious coryza vaccines containing a double-emulsion adjuvant system

The efficacy of experimental inactivated infectious coryza vaccines produced by a commercial vaccine manufacturer was evaluated. The vaccines, containing as the adjuvant phase either a double-emulsion mineral oil system or aluminum-hydroxide gel, were administered to 6-week-old chickens as a single dose. Some vaccines were a monovalent product containing a Page serovar C Haemophilus paragallinarum strain, and others were a bivalent product containing both Page serovar A and serovar C strains. After 3 weeks, all chickens were challenged by infraorbital sinus inoculation of virulent H. paragallinarum, either Page serovar C (strain HP31) or Page serovar A (strain HP14). The monovalent serovar C double-emulsion-based vaccines gave significant protection against a serovar C challenge, with the level of protection varying from 60% to 100%. The monovalent serovar C aluminum-hydroxide-gel vaccine also gave significant protection (94%) against a serovar C challenge. The bivalent double-emulsion vaccine gave significant protection against challenge from both serovars (100% for serovar C and 83% for serovar A). Although no major adverse reactions were detected, some chickens receiving both the double-emulsion vaccines and the aluminum-hydroxide vaccine developed relatively minor granulomatous reactions at the site of injection.