Duration of the protective immune response after prime and booster vaccination of yearlings with a live modified cold-adapted viral vaccine against equine influenza.

The research examines the longevity of the immune response of a live modified cold-adapted viral vaccine against equine influenza in young horses. The results demonstrated that the vaccine, administered in two doses, yielded significant protection from equine flu for up to a year.

Research Procedure

• The live vaccine, based on a reassortant cold-adapted strain, was earlier produced by the researchers. This vaccine incorporated surface proteins from the wild virus common in horses and internal proteins from a weakened strain.
• They evaluated the vaccine’s safety and the longevity of the immune response it generated. The experiment involved 90 young horses (yearlings) divided into groups, receiving different modes of vaccination or a control treatment.
• The vaccination modes included a single intranasal vaccination, two doses 42 days apart, or a control saline solution. Each mode was administered to distinct groups.

Vaccination Effect Validation

• A distinct set of animals from each group faced exposure to either a similar (homologous) or dissimilar (heterologous) strain of the influenza virus at various monthly intervals post-vaccination.
• They exposed one set of animals to the homologous virus at different time frames up to a year after vaccination.
• Another set of animals was exposed to a heterologous strain of the virus, a year after being vaccinated.

Findings and Conclusion

• The vaccine proved to be absolutely safe.
• A single dose of the vaccine provided significant clinical and virological protection from the homologous strain.
• However, only a double dose of the vaccine offered significant protection from the heterologous virus a year after vaccination.
• The vaccine also allows for distinguishing between horses that are infected and those which have been vaccinated.
• Based on these findings, the researchers recommend a double dose of intranasal administration of the vaccine, spaced 42 days apart, in veterinary practice.