Work

Longitudinal survey of 6-monthly booster vaccination-induced antibody responses to equine influenza A virus (H3N8) in Standardbred trotting horses in training

Year: 2026

Type: article

Abstract: Vaccination is an established and important tool in preventing the impact of influenza in the horse population but the frequency of booster vaccinations after the primary course of vaccinations to maintain protective antibody levels is still under debate. The aim of this field study was to monitor equine influenza antibody levels over the course of 13 months during which horses were given two booster vaccinations. Fifty-six vaccinated Standardbred trotters in training were monitored with monthly blood samples. The horses were routinely vaccinated with a commercial equine influenza vaccine 6 months apart, V1 and V2. Antibodies to vaccine strain A/equine/Borlänge/91 (Bor/91) were quantified by ELISA in all samples and also measured by single radial haemolysis (SRH) in samples obtained before and after V1. Mean titres against Bor/91 determined by ELISA were at the lowest level in the month prior to V1. All horses sampled immediately before and after V1 had an increase in titre except two ≥4-year-old horses. The antibody titres declined rapidly in the 3 months after V1. The boosting effect of V2 was lower compared to that of V1 and six horses with high pre-vaccination titres did not respond to V2, irrespective of age. Titres estimated by ELISA correlated well with antibody levels determined by SRH, which showed that while many of the horses would be unprotected before V1, antibody levels were boosted to protective levels after vaccination. Antibody responses were higher in horses with low antibody levels at booster vaccination compared to those with already high antibody levels. • Horses with low titres prior to booster vaccination showed the best responses. • High titres at booster vaccination carried a risk of low or no response. • Young horses seemed highest at risk of having non-protective titres prior to boost. • Tailored booster vaccination schemes, considering e.g. age, may be beneficial.

Source: Vaccine X

DOI: 10.1016/j.jvacx.2026.100778

Authors: Eva Wattrang, Helena Back, Louise Treiberg Berndtsson, Siamak Zohari, Janet Daly

Institutions: Swedish Veterinary Agency, University of Nottingham

Language: English

Topic: Influenza Virus Research Studies

Subfield: Epidemiology

Field: Medicine

Domain: Health Sciences

SDGs: Good health and well-being, Zero hunger

Open Access status: gold

Estimated APC paid: $2,440