Your veterinarian may discover changes in your cat's health that you have overlooked. It is always better to err on the side of caution. Vaccination Failures One of a cat owner's greatest frustrations occurs when a cat develops an infectious disease against which it has been vaccinated. There are five basic reasons for vaccination failure. The most common cause of vaccine inactivation is warming of the vaccine during shipping and handling.
Temperature control is critical to maintaining potency.
If the vaccine gets too warm during shipment to the distributor or while being stored at the distributor, it is inactivated. This is a common problem associated with vaccines purchased by mail or from feed stores. The buyer has no way to determine whether the vaccines were handled properly during shipment to non-veterinary suppliers. Veterinarians routinely refuse to accept shipments of vaccine if the vaccine is warm at the time of arrival. The vaccine for some of the feline respiratory viruses produces a high level of immunity, but that immunity lasts only 8-10 months in many cats.