Hi Evette,

Thanks for your question.

The possible side effects of any vaccine could be fever, lethargy and inappetence. These symptoms are not concerning since the purpose of the vaccine is to interact and challenge the immune system which creates this type of response. People receiving a vaccine will often experience these symptoms. A concerning vaccine reaction can occur in some pets that are sensitive to it and they could react with symptoms such as but not limited to facial swelling, urticaria or skin swellings, vomiting and itchiness. The timing of when these symptoms occur can be immediate or take a few days to develop since a patient could have an anaphylactic reaction or longer ‘cell-mediated’ reaction. An anaphylactic reaction can occur within seconds and create immediate skin reactions, difficulty breathing and can potentially be fatal. 15 years of giving vaccines and I have yet to experience such an event but every vaccine has its possible negative effects. These symptoms can be reduced or mitigated with treatment by your veterinarian with the use of antihistamines and steroids, or as your veterinarian recommends.

There is no way to predict whether an individual animal could be sensitive to a vaccine. Some believe that intensely inbred, or purebred cats could be at a greater risk of experiencing a reaction. Some breeds are known to be more reactive than others and you can discuss this with your veterinarian. If your cat is known to be allergic or has had previous reactions, you could discuss the concept of ‘splitting’ vaccines. This strategy could help reduce the chance of a vaccine reaction. It is well accepted that vaccination in both people and pets are more beneficial than they are harmful but it is hotly debated in the general public. I wouldn’t staunchly recommend vaccination without a conversation first about risk of exposure to the disease the vaccine is supposed to protect your cat against.

Don’t forget to discuss a preventative plan for the future. Look at the vaccines that were given and try to identify the one that may have caused the reaction. If there was a new vaccine given or if one was repeated for the first time, this might be the vaccine that created the reaction. You’ll want to discuss the risks and benefits of repeating that vaccine in the future. If that vaccine is protecting your cat from something very serious that they are at great risk of contracting, you can decide whether you go forward giving it in the future. Speak to your veterinarian about this and become informed so that you can make the decision for yourself.

In the end, your veterinarian is supposed to educate you in an unbiased way and allow you to make the decision. It’s so important that you work closely with your veterinarian to build a vaccination program for your individual cat and not just adopt the recommended series of vaccinations that are administered to all cats. At the same time, you have to remember that some vaccinations are labelled as core because they help to maintain control of a disease within a population of cats rather than just each individual cat. If everyone stopped giving a core vaccine, we would likely see a resurgence of that disease in the population much like history has shown us across populations of humans.

I encourage you to watch our videos about vaccination,“Which Vaccines Should I Give My Cat or Dog“, “Everything You Need to Know About Vaccine Reactions” and “How Often Vaccines Need Boosters and The Benefits of Titer Testing for Dogs and Cats” in preparation for a good conversation with your veterinarian.

I hope this helps.

Dr. Clayton Greenway