Inactivated Avian Infectious Bronchitis Virus Strains M41 and 4–91 Provide Broad Protection Against Multiple Avian Infectious Bronchitis Strains

<b>Background/Objective</b>: The poultry industry requires extensive vaccination of chickens against IBV in an effort to prevent the disease in animals and significant economic losses. Current vaccination strategies often lack effectiveness, and the continual emergence of new IBV variants makes disease control increasingly challenging. We have developed an inactivated vaccine for poultry containing nine different antigens (Nobilis Multriva), including two IBDV strains, two ARV strains, one NDV strain, one AMPV strain, one EDSV strain and two IBV strains: M41 (genotype GI-1) and 4-91 (genotype GI-13). In this study, the IB efficacy of this novel inactivated vaccine was investigated against homologous and heterologous IBV strains. <b>Methods</b>: Inactivated IBV vaccine containing the M41 and 4-91 strains (Nobilis Multriva) was administered intramuscularly, either alone or following vaccine priming, in SPF and commercial chickens. Birds were challenged with homologous and heterologous IBV strains at defined ages (peak of lay, mid-lay and end of lay). Vaccine efficacy was evaluated through serological assays, clinical observations, and monitoring of egg production post-challenge. <b>Results</b>: This vaccine provided excellent broad protection against different IBV strains circulating in different parts of the world, including IBV M41, 4-91, QX, Q1 and Var2. Furthermore, the vaccine provided long-lasting IBV serological response against IB M41 and IB 4-91 until at least 96 weeks of age in SPF and commercial layers and breeder birds. This vaccine will allow farmers to reduce the number of vaccination moments, thereby minimizing stress to the birds, while also decreasing labor demands and the risk of human error, ultimately contributing to lower overall vaccination costs. <b>Conclusions</b>: Given its demonstrated broad cross-protection and sustained serological responses, this nine-valent inactivated vaccine (Nobilis Multriva) represents a key component of an effective vaccination regimen for controlling IBV infections in the poultry industry.