Dog Behavior Change After Vaccination

The benefits of having your dog vaccinated typically far outweigh the risk of reactions to the vaccines. That said, some dogs do react to getting their shots. Here's more from our Las Vegas vets on the most common reactions to vaccines in dogs, and what to do if your dog reacts.

Why should I get my dog vaccinated?

Making sure your dog receives vaccinations early in life and on a regular basis as an adult gives them the best chance of living a long, healthy life. Rabies, hepatitis, and parvovirus are three illnesses that can be extremely expensive for pet owners and even fatal, particularly in puppies. It is always preferable to vaccinate against these diseases rather than treat your pet once they have manifested.

Typically the risk of your dog having a severe reaction to a vaccine is very low, and in most cases well worth the risk. 

Does my dog need all the available vaccines?

Your vet will consider the risk factors facing your dog based on your dog's breed, age, and lifestyle, then advise you on which immunizations are suitable for your dog. 

What are the most common reactions to vaccines in dogs?

Negative reactions are always a possibility with medical procedures, including vaccinations. It can be distressing for pet owners to see how their beloved pet reacts to vaccinations, but it's important to remember that most reactions are mild and temporary. Vaccinations can be less stressful for you and your dog if you are aware of the signs of a reaction and what to do if your dog displays them.


Vaccinated dogs typically experience lethargy and discomfort, and a mild fever is frequently present. Most of us would use the word "off" to describe this sensation.In this reaction, your dog's immune system is healthy and reacting appropriately to the vaccine. These minor symptoms should disappear within a day or two. If your dog is not feeling better within a few days, contact your veterinarian.

Lumps & Bumps

Like feeling "off," lumps and bumps are common reactions to vaccinations in dogs. The area where the needle was inserted into the skin or muscle may become tender following vaccination. The formation of these bumps is the immune system's response to the localized irritation.

Sneezing & Cold-Like Symptoms

While the majority of vaccines are administered via injection, the Bordetella bronchiseptica and parainfluenza virus vaccines are administered via nasal drops or sprays. These vaccines can cause symptoms similar to a cold, including coughing, sneezing, and a runny nose. The majority of dogs recover from these symptoms within two days. Consult a veterinarian if your dog develops more severe symptoms or does not recover within a few days.

Serious Reactions To Vaccinations

While most dog vaccine reactions are mild and short-lived, our canine companions can have more severe reactions that require immediate medical attention in rare cases.

Anaphylaxis - This severe allergic reaction can manifest as facial swelling, diarrhea, itching, hives, vomiting, and difficulty breathing. This type of severe reaction typically occurs immediately after your pet receives the injection (typically while you are still at the veterinarian's office), but it can occur up to 48 hours later.

Shock - The symptoms of shock following vaccines can include a slow heart rate, decreased blood pressure, and generalized weakness. You may also see a gray tongue and pale mucous membranes.

Can I prevent my dog from reacting? 

Vaccines help to protect the long-term health of your dog, and the risk of your dog having a serious reaction to a vaccine is very low. 

That said, if your dog has had a previous reaction to a vaccine, it is important to inform your veterinarian. Your vet may advise you to skip a particular vaccination in the future.

There is a slight increase in the risk of adverse vaccination reactions when multiple vaccinations are administered simultaneously. Smaller dogs may be particularly susceptible to this condition. To reduce the risk of adverse reactions, your veterinarian may suggest administering your dog's vaccinations over several days rather than all at once.

To learn more about vaccinations and preventive healthcare for your dog, contact our Las Vegas vets today to book an appointment.