You’re on your way to the vet and you’re wondering about possible reactions to the vaccine your cat will receive.
First, you should know that the vaccination will stimulate your cat’s immune system over an initial period of a few days. During this time, the body produces defenses called antibodies.
These antibodies will be the future soldiers inside your feline’s body, and it is this that will protect him if he comes in contact with one of these diseases (1).
So Dr. Franck, what can happen when I vaccinate my cat?
There are 3 possibilities…
Most animals will have no symptoms. You won’t see any change from his usual temperament.
Some mild signs are possible: some will simply feel more tired or eat a little less for 1-2 days.
A slight fever that will be temporary is also sometimes visible. Remember also that a little swelling or pain at the injection site is sometimes present. In all these cases, there is no treatment to do and these signs will disappear by themselves. A little patience and home care will be more than enough.
That being said, if the signs persist or if your cat’s condition deteriorates, it would be wise to contact your veterinarian.
Finally, there will be a small percentage of cats that will develop more severe symptoms called a vaccine reaction.
These reactions may appear within minutes or hours of a vaccine. This is called an acute allergic reaction. Some of the signs to watch for are: facial swelling, sustained diarrhea, repeated vomiting, marked weakness, difficulty breathing, excessive itching, and more than 2 days without eating anything.
If one or more of these signs are present, you must immediately consult the nearest veterinary clinic as you cannot treat this adequately at home (2).
Remember that the sooner these reactions are treated, the better the recovery will be afterwards.
You are now better equipped to identify a vaccine reaction.
As mentioned earlier, it is wise to contact your veterinarian if you see any signs that you find worrisome. Fortunately, the vast majority of vaccinations go smoothly and provide protection against many animal diseases.
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Source 1. Gershwin LJ. Adverse Reactions to Vaccination: From Anaphylaxis to Autoimmunity. Vet Clin North Am Small Anim Pract. 2018 Mar;48(2):279-290. doi: 10.1016/j.cvsm.2017.10.005. Epub 2017 Nov 29. PMID: 29195924; PMCID: PMC7114576.
Source 2. Shmuel DL, Cortes Y. Anaphylaxis in dogs and cats. J Vet Emerg Crit Care (San Antonio). 2013 Jul-Aug;23(4):377-94. doi: 10.1111/vec.12066. Epub 2013 Jul 15. PMID: 23855441.
Francis Lagacé has been a member of the Ordre des médecins vétérinaires du Québec since 2004. He practiced for 16 years in several veterinary clinics across Canada. He treated animals of all types, mainly cats, dogs and exotic animals (rabbits, rodents, ferrets, birds, reptiles). Since 2020 he has been working in the field of veterinary pharmacovigilance. You can find him on LinkedIn.