If the vaccine was at fault, the company that manufactured it could be liable for losses you incurred in treating Fido's bad reaction. Another possible source of liability might be the veterinarian who administered the vaccine, if he or she should have known it was defective but used the stuff anyway.

Your toughest task will be proving that the vaccine was defective. If you can, you may want to try small claims court.

If you cannot garner the proof you need, your only option may be to attempt to reason with the vet who gave the vaccine in the first place, emphasizing how humane it would be for him or her to spring for your losses -- and what a savvy business move, to boot.