This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Some of the most important developments in veterinary medicine over the past 20 years have been in the area of vaccinations against the most serious infectious diseases that can affect pet animals. Vaccinations offer a method of preventing an animal from contracting a disease - and some of the most important diseases which we can now protect our pets from are :

There are very few risks associated with vaccination, and the number of reported cases is extremely low. However, the recent observation that a type of tumour (called sarcoma) can occur at the injection site following some vaccinations (eg Feline Leukaemia Virus Vaccine) has increased awareness that there are potential risks , and it has resulted in all manufacturers re-evaluating their vaccination formulations and recommendations. The precise cause of sarcoma is currently being investigated, but it is thought to be a local reaction to a chemical (called an adjuvant) which is added to the vaccine to increase the protection stimulated in the patient.

Here is a list of potential risks associated with vaccines :

  • Allergic reactions to vaccines are uncommon , but they do occur occasionally, particularly after repeated doses of antiserum (eg to tetanus). Signs occur almost immediately after the vaccine is given, and can include :
    • Skin rash (weals) - called urticaria
    • Breathing difficulty
    • Vomiting
    • Diarrhoea
    • Increased salivation
    • Collapse
  • Live vaccines can be transmitted to other animals, in which they  may cause mild clinical signs
  • Some live vaccines can produce a latent infectious state in the vaccinated animal, making it a potential risk if it comes into contact with weak, debilitated or otherwise susceptible animals
  • Some live vaccines can cross the placenta and cause fetal abnormalities or abortion - so they should not be given to pregnant animals
  • Some vaccines cause a local, temporary swelling at the injection site
  • In some individuals the hair colour may change at the site of a vaccination - this is seen quite often in cats in which the hair at the vaccination site turns white
  • Some animals show mild clinical signs after they have been given a live vaccination eg some dogs cough after being given Kennel Cough vaccine by the intranasal route
  • Vaccines may not produce adequate immunity in some individuals, in which case the facts should be reported by your veterinarian to (in the UK) the Veterinary Medicines Directorate. In addition, there are certain circumstances under which a vaccine may be expected not work properly :
    • Ill animals should not be vaccinated because the vaccine may not work, and the animal is likely to be adversely affected by the vaccine
    • Animals should not be vaccinated within 4 weeks (and sometimes longer if a long-acting preparation has been given) of treatment with a corticosteroid or immunosuppressive drug as these may reduce the immune response in the patient


Updated October 2013