By Jennifer Coates, DVM
For the vast majority of pets, the benefits of appropriate vaccination far outweigh the risks, but as with any medical procedure, adverse reactions are always possible. Vaccine reactions are stressful and scary for pet parents but will be less so if you know what to watch for and how to react. Let’s look at three common reactions to vaccines and how to treat them, as well as several less-common conditions caused by vaccination.
The most common vaccine reactions that pets experience are lethargy and soreness, which may or may not be combined with a mild fever. This occurs because the body’s immune system reacts both locally and systemically to vaccine administration. Prompting the immune system to respond is the whole point of vaccination. If the pet comes in contact with the pathogen in the future, the immune system can now respond quickly and effectively, which reduces the chance that serious illness will result.
Thankfully, most pets are back to their normal selves within a day or two of vaccination. If your pet has more severe or prolonged soreness or lethargy, call your veterinarian. He or she can prescribe medications that will help your pet feel better.
Lumps and Bumps
When a vaccine is injected under the skin or into a muscle, a small, firm swelling may develop at the site because of local irritation and immune cells rushing to the area. The lump may be somewhat tender to the touch but should not grow (after the first few days), ooze, or become more painful as time passes. Unless any of these more serious symptoms are noted, just keep an eye on the area. Ordinary lumps and bumps associated with vaccines resolve on their own over the course of a few weeks. If this does not occur, make an appointment with your veterinarian.
Sneezing and Snuffling
Most vaccines are given by injection, but a few are administered through drops or a spray squirted into the nose. The most commonly used intranasal vaccines are Bordetella bronchiseptica and parainfluenza virus for dogs and feline rhinotracheitis (herpes virus) and calicivirus for cats. Intranasal vaccines were developed, in part, because these diseases are all respiratory in nature and pets can become infected through their noses. Therefore, it makes sense to give a nasal vaccine to encourage immunity to develop at the first spot where an infection might develop. However, it’s not too surprising that adverse reactions associated with the respiratory tract are also possible.
Pets may sneeze, cough, or develop stuffy/runny noses for a few days after intranasal vaccines. Some veterinarians will also apply a drop of the feline vaccine into each of the cat’s eyes. In these cases, cats may also develop red, runny eyes. Mild sores within the mouth are also possible with the intranasal cat vaccine. These types of symptoms should resolve on their own within a day or two. If that is not the case, call your veterinarian for advice.
Less Common Vaccine Reactions
On rare occasions, pets will have more serious reactions to vaccines. A potentially life-threatening allergic reaction called anaphylaxis is one of the scariest. Soon after vaccination (usually minutes to hours), a pet undergoing anaphylaxis typically develops hives, itchiness, facial swelling, vomiting, diarrhea, and/or difficulty breathing. Additionally, any type of injection can lead to infection or abscessation if bacteria are able to gain entry to the skin or underlying tissues. Signs to watch for include discolored skin (often red), discomfort, discharge, and swelling.
Research is not completely clear on the matter, but there may be some relationship between vaccination and the subsequent development of immune-mediated diseases. Symptoms will vary with the specific type of disease involved. A more definitive association between vaccination and an aggressive type of tumor at the injection site in cats has been established, but the incidence is quite low: approximately one case per 10,000 to 30,000 vaccinations, according the American Veterinary Medical Association.
If you suspect that your pet is having a serious adverse reaction to vaccination, contact your veterinarian immediately.
Preventing Vaccine Reactions in Pets
It is important to remember that for the vast majority of pets, vaccination will not result in a significant adverse reaction but will protect against potentially serious diseases. That said, if your pet has previously had a bad reaction to a vaccine or has underlying health problems, talk to your veterinarian. It may be in your pet’s best interests to change or even skip certain vaccines that would otherwise be given.
Research has shown that the risk of mild vaccine reactions (lethargy, soreness, fever, etc.) does increase when multiple vaccines are given at the same time, particularly in young adult, small-breed, neutered dogs and in young adult neutered cats. Only you can decide if lessening this risk is worth the added stress of multiple vet visits.