What is the clinical evidence from this study?

Study design: Other. Population: Infectious bronchitis virus (IBV) (n=90). Intervention: vGA08 and Mass type IBV vaccines vs. Non-vaccinated. Primary outcome: Amount of challenge virus detected at 5 days post-challenge (1 to 3-log reduction, p=<0.05).

What question did this study set out to answer?

To evaluate the efficacy of two vaccines, vGA08 and Mass type, against multiple IBV antigenic variants in poultry.

March 17, 2026Open Access

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

Q: What are the key findings of this study?

Simultaneous vaccination with vGA08 and Mass vaccines significantly reduced clinical signs and decreased challenge virus load by 1 to 3 logs against four circulating IBV variants compared to no vaccination.

Q: What question did this study set out to answer?

To evaluate the efficacy of two vaccines, vGA08 and Mass type, against multiple IBV antigenic variants in poultry.

Key Result

Simultaneous vaccination with vGA08 and Mass vaccines significantly reduced clinical signs and decreased challenge virus load by 1 to 3 logs against four circulating IBV variants compared to no vaccination.

Key Points

To evaluate the efficacy of two vaccines, vGA08 and Mass type, against multiple IBV antigenic variants in poultry.
Administered vGA08 and Mass type vaccines simultaneously to chicks at one day old.
Challenged vaccinated and non-vaccinated birds with four different IBV variant strains at four weeks old.
Assessed clinical signs and virus levels in both groups post-challenge.
Vaccinated birds showed reduced clinical signs compared to non-vaccinated ones.
The level of challenge virus detected was significantly lower in vaccinated birds across all variants.
Findings suggest effective cross-protection provided by the tested vaccines against current IBV strains.

Structured PICO

Does simultaneous vaccination with vGA08 and Mass type IBV vaccines reduce clinical signs and viral load in chickens challenged with circulating variant IBV strains?

Population

90 specific pathogen free (SPF) chickens

Intervention

Simultaneous vaccination with vGA08 and Mass type IBV vaccines by eye-drop at 1 day of age, followed by challenge with 4 different IBV variant strains (PA/1220/98, CA/1737/04, NC/DARK/23, and Canada/DMV1639/23) at 28 days post-vaccination

Comparator

Non-vaccinated chickens challenged with the same variant strains (positive controls) and non-vaccinated, non-challenged chickens (negative controls)

Outcome

Clinical signs (respiratory scores) and challenge virus detection (viral genome copies/ml) in choanal swabs at 5 days post-challengesurrogate

Simultaneous vaccination with vGA08 and Mass type IBV vaccines provides significant cross-protection against four currently circulating variant IBV strains in poultry.

Main Result

Effect estimate: 1 to 3-log reduction

p-value: p=<0.05

Limitations

Heterologous cross-protection does not guarantee complete immunity.
Birds can still become infected with the heterologous field virus and can exhibit mild clinical signs.
The exact mechanism underlying cross-protection remains unclear.

Abstract

Abstract 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.

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