Efficacy of a non-updated, Matrix-C-based equine influenza subunit-tetanus vaccine following Florida sublineage clade 2 challenge.
Authors: Pouwels H G W, Van de Zande S M A, Horspool L J I, Hoeijmakers M J H
Journal: The Veterinary record
Summary
# Editorial Summary Current equine influenza vaccines contain strains that have not been updated since the 1990s, raising concerns about their protective capacity against modern field strains; this 2014 trial evaluated whether a Matrix-C-adjuvanted subunit vaccine (EquilisPrequenza Te) could provide meaningful cross-protection against the Florida sublineage clade 2 virus (A/eq/Richmond/1/07), which had emerged after the vaccine antigens were selected. Seven previously unvaccinated, seronegative horses received two doses of the vaccine four weeks apart, whilst five controls remained unvaccinated; all horses were then challenged three weeks later via aerosol with the heterologous strain and monitored for clinical signs, temperature changes, viraemia and viral shedding over 14 days. Vaccinated horses showed significantly reduced clinical and total clinical scores compared to controls, and whilst viral excretion still occurred in both groups, vaccination substantially curtailed both the duration and total quantity of virus shed (with statistical significance across all measured virological parameters). Although the vaccine did not completely prevent infection or shedding, the marked reduction in clinical disease severity and viraemic load suggests the Matrix-C adjuvant formulation may confer broader cross-protection than older vaccine platforms—a finding of considerable practical importance given that equine influenza continues to evolve and field strains frequently diverge from vaccine antigens.
Read the full abstract on PubMed
Practical Takeaways
- •Current equine influenza vaccines can provide meaningful cross-protection against emerging strains even when not specifically updated for new variants—vaccinated horses had minimal clinical signs and substantially reduced viral shedding
- •The Matrix-C adjuvant platform appears to support cross-protective immunity; vaccinated horses showed reduced fever and clinical disease compared to unvaccinated controls after challenge
- •Regular vaccination remains worthwhile for reducing disease severity and transmission risk even when vaccine strains don't perfectly match circulating field strains
Key Findings
- •Vaccinated horses showed significantly lower clinical scores (P=0.0345) and total clinical scores (P=0.0180) compared to controls following challenge
- •Vaccination significantly reduced virus excretion extent (P=0.0006), duration (P<0.0001), and total viral load (P=0.0006)
- •A non-updated Matrix-C-based equine influenza subunit vaccine demonstrated cross-protective capacity against a heterologous Florida clade 2 challenge strain
- •Vaccination significantly affected the likelihood of virus positivity during the study period (P=0.0017)