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Vaccination reactions in pets

isolated pets

Overview

  • Vaccinations (like any other medicine) can sometimes cause side effects.
  • Fortunately, side effects are rare, usually mild and pass within a few days. Severe vaccine reactions are very rare.
  • Contact your vet if your pet is suffering side effects after a vaccination.
  • Contact your vet immediately if your pet is having an allergic reaction.
  • It’s important to remember that millions of pets are vaccinated each year and only a very small number experience side effects.
  • Vaccination is an excellent way to prevent disease and the benefits far outweigh the possible risk of side effects.

Covid-19 update

At the moment, your veterinary practice may be unable to offer routine procedures such as booster vaccinations. Read our advice on how to keep your dog, cat and rabbit safe if they miss a vaccination during lockdown.

Vaccine reactions explained

When we vaccinate against a disease, we give a tiny amount of the disease to encourage the immune system to create antibodies to it (but not enough to cause illness). Once your pet has created antibodies, they will have some immunity and be ready to fight if they encounter the disease again. As with any other medicine, it’s possible for pets to have an allergic reaction to a vaccine, but it’s important to remember that this is extremely rare. Vets vaccinate millions of pets each year and only a tiny number experience side effects, most of which are mild and pass within a few days.

Vaccination is a very effective way of preventing disease and the benefits far outweigh the possible side effects.

If you are concerned that you pet is at a higher risk of having a vaccine reaction, for example if they are old or unwell, discuss the risks with your vet to help you make an informed decision about whether to vaccinate or not. In many cases, it’s wise to vaccinate vulnerable pets because they are at a higher risk of catching infectious disease.

Common vaccine side effects

There are some common vaccine side effects that often only last a few days and disappear without treatment:

  • Low energy (lethargy)
  • Eating less
  • Sleeping more
  • Fever (high temperature)
  • Mild swelling around the vaccine site that disappears in two - six weeks.

Less common side effects include:

  • Twitching
  • Itchy skin
  • Vomiting
  • Diarrhoea
  • Limping.

Rare vaccine side effects

In very rare circumstances, a vaccine can cause a severe allergic reaction (anaphylaxis). Symptoms of a severe allergic reaction include:

  • Swelling anywhere on the body
  • Breathing difficulty
  • Cold ears, legs and feet
  • Seizures
  • A pounding heart beat
  • Collapse.

Take your pet straight to the vets if they are having a severe allergic reaction. If possible, try to phone your vets on the way so they can prepare for your arrival.

When to contact your vet

If your pet is suffering mild side effects after a vaccination, monitor them and call your vet for advice if you are concerned, if their condition gets worse, or if their symptoms last for more than 24-48 hours.

Contact your vet immediately if your pet is having an allergic reaction.

Why vaccinate?

Negative media coverage around vaccination side effects in recent years has raised concerns for many people. However, it’s important to remember that the benefits of vaccination far outweigh the small risk of a vaccine reaction.

Vaccinations have been so effective in recent times, that we hardly see some of the diseases we vaccinate against anymore. However, we do still see them in areas where vaccination rates are low. If we all stopped vaccinating our pets it would only be a matter of time before we started to see a rise in the diseases we can easily protect against, and in many cases these are very serious diseases which can be fatal.

Feline injection site sarcomas

Cats have a very small risk of injection site sarcomas (a type of cancer that forms underneath the skin) at the injection site of a vaccine, microchip or medicine. These are very rare speak to your vet for more information.

Published: April 2020

PetWise Pet Health Hub – brought to you thanks to support from players of People’s Postcode Lottery 

Written by vets and vet nurses. This advice is for UK pets only.

Illustrations by Samantha Elmhurst