Any horse coming to my farm is quarantined....for their own good, as well as that of the others. They are subject to different germs in both cases. Even show stock -- after all, even tho they get more frequent and sometimes more extensive vaccines, they have been exposed. Safety is all.
So, whatever your decision now or later, consider that.
Many years ago I have 2 animals at an auction, brought home as I no saled....quarantined. There had been an animal at the sale who was caughing profusely, not snotty or anything. A red flag went up even though they were at the far end of this barn. Sure enough, 3 days later both had pneumonia!! Treated, etc. No others of my 60 at home got it but, only because I used caution.
I carry alcohol based wipes in my car, keep it in the barn, bleach travels with me for shoe soles. You never know where you will be or the situation. This is true with people issues, not just animal. Good vets will attest to this as well as practice it!