Immunity to equine influenza: relationship of vaccine-induced antibody in young Thoroughbred racehorses to protection against field infection with influenza A/equine-2 viruses (H3N8).

Authors: Newton J R, Townsend H G, Wood J L, Sinclair R, Hannant D, Mumford J A

Journal: Equine veterinary journal

DOI: 10.2746/042516400777612116 PubMed: 10661388Log in to save

Summary

# Editorial Summary During influenza outbreaks affecting vaccinated Thoroughbreds in Newmarket (1995–1996), Newton and colleagues used nucleoprotein ELISA and serological testing to examine the relationship between vaccine-induced antibody levels and field protection against equine influenza A/H3N8. Their investigation demonstrated a strong correlation between serum single radial haemolysis (SRH) antibody titres and clinical protection, validating earlier experimental aerosol challenge models and confirming that antibody measurements reliably predict real-world immunity. Yearlings showed antibody profiles consistent with established vaccine response patterns, whilst horses already in training maintained higher pre-revaccination antibody levels, though this raised an important question about optimal timing of boosters. The findings suggest that routine serological monitoring post-vaccination could identify individual poor responders and susceptible periods between doses, enabling practitioners to refine vaccination protocols and close gaps in protection—particularly valuable for high-risk populations such as yearlings entering training and racehorses at stud yards where influenza transmission poses significant welfare and economic costs.

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Practical Takeaways

•Monitor serum antibody levels (SRH) post-vaccination to identify horses with inadequate immune responses before they face field exposure, particularly in high-risk yearlings and horses entering training.
•Vaccination strategy should account for age-related immune responses—yearlings and horses in training may have different susceptibility windows requiring tailored revaccination timing.
•Consider serological surveillance as a practical tool to time revaccinations strategically rather than relying on fixed schedules alone, especially during outbreak periods.

Key Findings

•Serum levels of vaccine-induced SRH antibody correlated closely with protective immunity against equine influenza A/H3N8 in field outbreaks.
•Yearlings showed antibody profiles consistent with experimentally derived vaccine response models used in licensing studies.
•Horses in training had higher pre-revaccination antibody levels than yearlings, suggesting different susceptibility windows.
•Serological monitoring can identify susceptible periods and poor vaccine responders to optimize vaccination strategies.

Conditions Studied

equine influenza a/h3n8vaccine responsefield infection in racehorses

Related References

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