For those of you who vaccinate your own horses....i have a question regarding the Botulism vaccine...i purchased a few 5 dose vials last season and still have about half a vial left in my fridge-still w/in expiration date....i have a new horse that i need to start the vaccine on..however i read on the vial that it states once the vial has been opened you must use all of the contents?

Obviously that didn't happen in my case....have any of you still used any left over portion remaining...its been refrigerated and still is w/in plenty of time on expiration?

I sort of remember my vet leaving me w/ a vial a few years ago to finish out the series...as its a 3 dose protocol-obviously i don't think i used it all up at once..but can't say for certain