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 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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  • It also depends on the manufacturer of the vaccines. All vaccines are not equal. I have received some information that panleukopenia 3 in 1 vaccines produced in Greece had a very high percentage of adverse reactions resulting in the deaths of whole litters of kittens. Also that a Fort Dodge laboratory in Ireland was closed down because of chronic poor quality vaccines.

    • Thanks Harvey. Good points. I believe we should have good information provided by our vets on the vaccines they use. I don't believe the average customer enquires enough. I asked my vet about the risk and she said there was a risk but it would have been great if she had told me there was a 1 in 1000 chance of inflammation or whatever - something far more precise. That would have been fantastic. But nothing and my vets are good.

  • Interesting Michael I've been calculating as I've only ever had 1 cat suffer an allergic reaction and that was Ozzie at his last jab; his whisker pads just ballooned up and part of his face, his breathing laboured I had to rush him off to the emergency vets.

    If I calculate the amount of cats we've had and x by how many injections they've had I can confirm that equates to 1 in 113.

    • Leah, you have provided some hard stats from personal experiences. Great. The figure is high but I'd like our vets to provide more stats. I think they owe us a duty to provide the information. I'd bet none of them do.

      • I would imagine its much higher because I bet a lot of cases go unreported. Something I didn't realise which the emergency vet told me 'if this happens again you can give your cat half a Piriton but not the non-drowsy one just the normal one; the non-drowsy would kill them' I thought Ah thanks for that after you charged me £122 lol

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