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Overview
The type of killed infectious Coryza vaccine given to young pullets can affect how much muscle damage occurs at the injection site and how well birds grow after vaccination, according to research conducted by Fernando Ruiz-Jimenez, Zoetis technical services veterinarian.
Based on the findings, Ruiz-Jimenez recommends that producers start young pullets on an aluminum hydroxide vaccine to prime the immune system with less risk of muscle damage, then follow up with the oil-based vaccine at approximately 12 weeks when birds are better able to handle it.
“Keep those birds building their frame and don't set them back that much with the first shot,” he said. “Then when they're older, they can handle the oil vaccine a lot better — and that's when you get your long-term protection going into production.”— Fernando Ruiz-Jimenez
He emphasized that under high disease pressure, two doses are essential. One dose alone has not proven sufficient to carry birds through a strong challenge.
Coryza Affecting Younger Birds
Infectious Coryza has traditionally been a problem in older birds. However, in recent years, flocks as young as five weeks of age in Ohio, Indiana and Pennsylvania have been affected, forcing producers to vaccinate earlier than planned.
According to Ruiz-Jimenez, the challenge is younger birds don't tolerate killed vaccines as well as older ones. Vaccinating too early can cause serious muscle damage at the injection site or mortality but waiting too long to vaccinate leaves birds exposed to the disease.
Oil-Based vs. Aluminum Hydroxide-Based Vaccines
All killed vaccines contain an ingredient called an adjuvant, which is a substance that helps the immune system respond to the vaccine. The two main types used in commercial Coryza vaccines are oil-based and aluminum hydroxide-based formulations.
Oil adjuvants tend to produce a stronger, longer-lasting immune response but are harder on birds, Ruiz-Jimenez explained. Aluminum hydroxide adjuvants are gentler but may not protect birds as long.
The difference in tissue response between adjuvant types is well established in poultry research.
A 2024 review published in the National Library of Medicine found that oil-based adjuvants can compromise meat quality through an immune response known as granuloma formation at the injection site. Additionally, aluminum salts carry their own risk of inflammation and granuloma formation, even though they can be considered safer.
Research on Salmonella vaccines, where adjuvant reactivity is also a concern, has shown that mineral oil adjuvants can affect the quality of the immune response and the severity of reactions at the injection site if not properly formulated.
Coryza Vaccination Study
A research project tested four combinations of the two vaccine types across 135 Leghorn pullets, with the first dose given at seven weeks and a booster at 12 weeks.
Birds that received the oil-based vaccine — particularly those that got it for both doses — had the most severe muscle damage. Birds that received the aluminum hydroxide vaccine as the booster, regardless of which vaccine they received first, had significantly less muscle damage and gained more weight in the two weeks following the booster compared with birds given the oil vaccine as the booster.
Weight gains after the first dose were similar across all groups, suggesting the first shot, regardless of type, does not meaningfully affect weight gains after vaccination, he continued.
What's Next
Ruiz-Jimenez said he is planning a follow-up study to determine how long protection lasts under each vaccination program, as the research focused on tissue reaction and weight gain, not immunity duration.
“We only assume that the aluminum vaccine will give shorter-term protection, but we don't know to what extent,” he said. “Our next step is to find out.”— Fernando Ruiz-Jimenez