The impact of different equine influenza vaccine products and other factors on equine influenza antibody levels in Thoroughbred racehorses.
Authors: Ryan M, Gildea S, Walsh C, Cullinane A
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Influenza Vaccination and Antibody Response in Racehorses Vaccination strategy for equine influenza in training yards remains under-researched, prompting Ryan *et al.* to investigate how vaccination history and other factors influence serological protection in Thoroughbreds. Blood samples from 102 vaccinated racehorses in a single training establishment were tested one month post-booster vaccination using single radial haemolysis, with vaccination records cross-referenced against official passports and analysed using multivariate statistics. Counterintuitively, whilst horses receiving multiple *different* vaccine products demonstrated significantly higher antibody titres, those with greater *numbers* of total doses showed lower responses; females also mounted substantially stronger antibody responses than males, and most horses (95%) had received more than one vaccine type during their careers. These findings suggest that vaccination protocol should balance the protective benefits of product rotation with avoiding excessive booster frequency, whilst recognising sex-based differences in immunological response that may warrant sex-specific vaccination strategies in high-risk populations. The wide variation in vaccination practice observed (32% receiving three different products, with mean inter-booster intervals of 7.7 months) highlights the need for evidence-based guidance to optimise immunity without compromising welfare through over-vaccination.
Read the full abstract on PubMed
Practical Takeaways
- •Sex of the horse influences serological response to equine influenza vaccination, with females mounting better antibody responses—consider this when interpreting vaccination efficacy
- •Using different vaccine products over time may provide better immune protection than repeated doses of the same product, but excessive vaccination doses do not guarantee higher protection
- •Vaccination strategy should account for individual factors (age, sex, previous products used) rather than applying one-size-fits-all protocols to all racehorses in training
Key Findings
- •Female racehorses demonstrated significantly higher antibody levels against equine influenza compared to males following booster vaccination
- •Horses receiving multiple different vaccine products (95% received >1 product, 32% received 3 products) showed higher antibody levels than those with fewer products
- •A negative association was found between total number of vaccine doses received and SRH antibody titre, suggesting diminishing returns with repeated vaccination
- •Average vaccination interval was 7.7 months with over 70% of horses receiving their first dose between 6-12 months of age