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Vaccination and a sensible biosecurity policy, in partnership, are the key to best prevention for EI infection.

Vaccination is of primary importance to help safeguard horse health and welfare and to help protect equine businesses. All equine animals in UK should be fully and properly vaccinated as it is our most effective tool in the prevention and control of EI. No vaccines against EI, nor any other infections, are 100% protective and influenza vaccines, for all species, including humans, are recognised to be unable to fully protect against the continual viral genetic changes (‘antigenic drift’) that occur naturally. Nevertheless, it is clear that even during the 2018/2019 EI outbreaks reported throughout Europe, including UK, whilst infection did occur in the occasional vaccinated horse, clinical signs were either absent or much milder and infected animals recovered more quickly with fewer cases of secondary pneumonic complications. That being the case, viral shedding and aerosol spread to other horses would have been reduced. It was also clear that horses that were last vaccinated within 6-months of challenge, were at less risk of succumbing to infection, when challenged, than those that were last vaccinated at longer intervals. It is recommended that all horses resident on all stud farms are fully vaccinated at least in accordance with the datasheet requirement of the specific EI vaccine, as recommended by the attending veterinary surgeon, but recognising that younger animals intended for racing will need to comply with racing’s regulatory requirements for EI vaccination. This will usually include vaccine manufacturers recommending a primary course of 2 doses administered 4-6 weeks apart, followed by a first booster 5 months after the second primary dose, with at least annual boosters thereafter. As noted above and following experience in the 2018/2019 outbreak, booster vaccinations are now being recommended every 6 months rather than annually. See Appendix 8 for vaccine details.

It is recommended that in order to provide optimal antibody levels in colostrum pregnant mares are booster vaccinated for EI approximately 4-6 weeks prior to their predicted foaling date, with their tetanus vaccine booster, using a combined vaccine. Foals that receive adequate maternal antibody should not commence their own vaccination programmes until they are at least 6 months of age when maternally derived antibody from colostrum has adequately declined and will not interfere with the foal’s immune response to vaccination.

NB From 1 January 2022 the British Horseracing Authority revised EI vaccination requirements will apply to all equines entering racecourse property.