Vaccine Reactions

Although vaccination programs are designed to keep your pet healthy, some pets may experience side effects after they have been vaccinated.

Common side effects include:

  • injection site tenderness
  • lethargy
  • fever
  • a small lump or bump at injection site.

These side effects, though annoying, may actually indicate an appropriate immune reaction is occurring. This means that your pets’ immune system has recognized the vaccination as a foreign virus and in return mounted an immune response to that virus. If your pet comes into contact with this virus in the future, the immune system is “wise” to it and your pet may resist severe infection.

Generally, these common side effects last only 1-2 days post vaccination. If your pet is experiencing side effects longer than that, or the side effects seem severe, they should be seen by a veterinarian as soon as possible.

Emergency side effects that may rarely occur:

  • vomition
  • seizure
  • collapse
  • wheals, hives and facial edema or swelling.

Emergency side effects generally occur within the first five minutes or within the hour after vaccination.  If your pet experiences an emergency side effect veterinarian antihistamines, corticosteroids, epinephrine and supportive care may be needed immediately. Based on the severity of the reaction combined with the consideration of your pet’s lifestyle, you and your veterinarian can decide whether or not your pet should be vaccinated again. Sometimes, pre-medication (given before the vaccinations) can prevent these reaction.  If your pet has had these reactions to vaccines in the past, inform any veterinarian at each and every visit of that fact.  If you have any questions after your pet has been vaccinated, do not hesitate to call your veterinarian.