The risk of an adverse reaction to vaccinations in cats

We know that vaccinations are important to prevent disease in our cats. However, we also know that vaccinations carry a risk for a cat but how great is it? It would be nice to know the exact risk that we put our cat through when we ask a vet to vaccinate him so that we can give informed consent.

And this is where the difficulty arises. My research on the Internet indicates that it is difficult to find statistics about the percentage of cats who suffer adverse reactions.

Certainly, veterinary sites on the internet specify the sort of adverse reactions that a cat might suffer but in almost every example they do not specify the percentage of cats which suffer them.

Cat Vaccination. Photo: The Answer Vet

However, the answers that I was seeking were found when searching using Google Scholar, a specialist section of Google search but are they reliable statistics?

On the AVMA website they have a report entitled “adverse events after vaccine administration in cats… 2002-2005.

They state that when 496,189 cats were vaccinated with 1,258,712 vaccine doses there were 2560 vaccine-associated adverse events. In percentage terms this means that 0.5% (one half of one percent) of cats suffered adverse reactions. Put that another way it means that 1 cat in every 200 suffered a reaction according to the AVMA study.

In another AVMA study published on their website they state that when 31,671 cats were given 61,747 doses of vaccine, there were 73 cats who suffered post-vaccine inflammation. Post-vaccine site cancers developed and 2 cats. This means that 0.23% of cats suffered inflammation. This is about 1 in 400. As for cancers the percentage is almost negligible.

Based on these very low figures, concerned cat caretakers will opt for vaccinations because the benefits far outweigh the negatives.

However, I have to mention some information on another website (which I consider to be reliable) in which the author refers to a study of more than 2000 cats and dogs in the UK. The study was carried out by Canine Health Concern. It showed a 1 in 10 risk of adverse reactions from vaccines. This means that 10% of cats suffer a reaction. This starkly contradicts the AVMA findings.

It also contradicts the vaccine manufacturer’s report concerning adverse reactions. They say that “less than 15 adverse reactions in 100,000 animals vaccinated”. This is 0.015% or 1 cat every 6,666. The site also states that adverse reactions in small animals are 10 times higher than in larger animals because small animals are being over-vaccinated. The author refers to “breeds” but I believe she means both purebred and non-purebred animals.

At the time of writing this, I do not have any more information about the risk of adverse reactions to vaccinations in cats but officially the rate is very low although unofficially they are much higher so I am somewhat confused. Perhaps there is a requirement for an independent, authoritative, study?

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Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in a many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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