Christine King BVSc, MANZCVS (equine), MVetClinStud
Hendra: why not just go ahead and vaccinate?
This one is short and sweet. The benefit to getting and keeping your horse vaccinated against HeV is that you won't run into the problem of vets refusing to come out, or equine hospitals refusing entry, just because your horse isn't currently vaccinated against HeV.
Along the same lines, you won't be refused entry to equestrian events just on the basis of your horse's HeV vaccination status.
Only you can decide on the weight to give this particular benefit.