Field studies on equine influenza vaccination regimes in thoroughbred foals and yearlings.
Authors: Cullinane A, Weld J, Osborne M, Nelly M, Mcbride C, Walsh C
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Equine Influenza Vaccination in Young Thoroughbreds Cullinane and colleagues conducted three field-based investigations into how Thoroughbred foals and yearlings mount immune responses to different influenza vaccination protocols, measuring protective antibody levels (haemagglutinin) via haemagglutination inhibition testing. Maternal antibodies present at vaccination proved problematic: repeated dosing in their presence appeared to induce serological tolerance rather than enhance immunity, suggesting that timing vaccination around maternal antibody clearance may be critical. When comparing vaccine formulations, monovalent subunit vaccines significantly outperformed both ISCOM and multivalent products (which included equine herpesvirus and reovirus), indicating that vaccine complexity inversely correlated with influenza-specific immune response. An additional booster dose administered between the standard second and third vaccinations improved antibody levels in young horses, supporting a more frequent dosing schedule than manufacturers originally recommended and aligning with racing regulations in certain jurisdictions. Although specific vaccines have since been updated with contemporary virus strains, these findings establish enduring principles for optimising vaccination responses in young stock—particularly regarding maternal antibody interference, monovalent formulation superiority, and the benefits of accelerated booster protocols during the critical developmental period.
Read the full abstract on PubMed
Practical Takeaways
- •Consider timing of vaccination programs in foals with maternal antibodies present, as repeated early vaccination may be counterproductive
- •Monovalent influenza vaccines appear more immunologically effective in young horses than multivalent formulations
- •Adding an extra booster vaccination improves protective antibody levels in young racehorses, which may justify the additional cost and handling
Key Findings
- •Repeat vaccination in the presence of maternal antibodies may induce serological tolerance in foals
- •Monovalent influenza vaccine produced significantly better immune response than ISCOM or multivalent vaccines containing equine herpesvirus and reovirus
- •An additional booster vaccination between the second and third doses provides benefit to young horses beyond manufacturer recommendations