INFLUENZA VACCINE DECISIONS
Bringing horses together from different regions of the world for competition increases the risk of Equine Influenza outbreaks due to mixing of horses in confined quarters, exposure to new and different viral strains and the suppression of immunity experienced by intensely exercising horses [14, 21, 22, 23].
It is important to remember that vaccination is an exercise in risk management and does not provide impunity from incurring or spreading disease . There is wide variance in the efficacy of different vaccines, vaccination protocols and response of individual animals to vaccination. Overall vaccination with effective vaccines reduces the chances of an animal developing clinical disease when exposed to Equine Influenza or once infected, from spreading the virus to other animals [2, 4].
Current research indicates that modified live intranasal vaccines, which induce both humeral, cell mediated and local mucosal immunity with a broad spectrum of whole virus antigens, produce the most robust and durable protection against emerging strains [3, 4, 17, 18].
Recombinant vectored vaccines induce both humeral and cell mediated immunity for strains similar to the incorporated recombinant surface antigens .
Although some killed virus vaccines can provide effective immunity via humeral antibody protection alone, care must be taken to ensure that current strains of both European and American lineages are incorporated into the vaccine [2, 3, 4, 15, 17, 24, 25, 26, 27]. If using a killed vaccine, the following advice should be considered:
“The current recommendation of the Expert Surveillance Panel on equine influenza is that vaccines contain an A/eq/South Africa/4/2003 (H3N8)-like virus (American lineage) and an A/eq/Newmarket/2/93 (H3N8)-like virus (European lineage). The presence of H7N7 equine influenza virus strains (i.e. A/eq/Prague/56 or A/eq/Newmarket/77) in vaccines is not recommended any more” .
The FEI requirement for booster vaccinations every 6 months following the primary course is a sensible approach due to the limited duration of immune response stimulated by vaccination . Timing the booster to occur as close as possible to the start of the competition season or event will provide maximum benefit.
Always consult with your veterinarian before embarking on a vaccination program for your horse.