Cross-protection studies using vGA08 and Mass type IBV vaccines against four different antigenic variant viruses currently circulating in poultry in the USA and Canada

Infectious bronchitis virus (IBV) is a highly contagious gammacoronavirus that causes disease in chickens, typically presenting with respiratory signs but in some cases affecting the reproductive or renal systems. Due to different antigenic variants co-circulating in poultry with limited availability of homologous vaccines, producers have historically combined different vaccine types to provide a broader cross-protective immunity. This study evaluated whether two USDA licensed vaccines (vGA08 and Mass types-administered simultaneously at one day of age) can protect against challenge with 4 different currently circulating variant IBV strains in the US and Canada (PA/1220/98, CA/1737/04, NC/DARK/23, and Canada/DMV1639/23) at 4 weeks of age. For the vaccinated/challenged birds, clinical signs were reduced and the level of challenge virus detected was significantly lowered for each of the challenge viruses compared to non-vaccinated birds challenged with the same virus. This study is important because it provides poultry veterinarians with information on the level protection that can be expected using safe and efficacious commercially licensed vaccines against 4 currently circulating variant IBV strains.