What are the side effects of dog vaccines?
Updated By PetymFacts checked against official sources on
Quick answer
WSAVA says the common ones are mild: pain or swelling at the injection site, tiredness, a poor appetite, a mild fever or a bout of vomiting. Serious allergic reactions, such as facial swelling, hives, repeated vomiting, breathing trouble or collapse, are less common and usually start within minutes to an hour. They need a vet at once.
Reactions are uncommon overall: a US study of more than 1.2 million dogs recorded 38 per 10,000 dogs vaccinated within three days. Small dogs given several vaccines at one visit had the highest risk, so tell your vet if your dog has reacted before.
Which reactions after a vaccine need a vet now?
Call your vet or go to the nearest 24-hour vet if you see any of these, especially in the first hour.
If Swelling of the face, muzzle or eyes, or raised itchy bumps (hives) on the skin.
Go back to the vet now. WSAVA lists severe hives and facial swelling among the serious reactions vets plan around. WSAVAstudy
If Collapse, weakness, pale gums or difficulty breathing within minutes of the injection.
This may be anaphylaxis, an emergency. In a Japanese study WSAVA reports, every case began within 60 minutes and almost half within 5 minutes. WSAVAstudy
If Vomiting or diarrhoea that keeps coming back.
Call your vet the same day. A single episode can be a minor reaction, but repeated bouts need checking. WSAVAstudy
If A swelling at the injection site that grows, is very painful or does not settle.
Show it to your vet. Swelling is a common local reaction, but your vet should check one that changes. WSAVAstudy
If Your dog stays unwell, seems to get worse, or stops eating altogether.
Call your vet. The WSAVA guidelines say some reactions can appear hours or longer after vaccination. WSAVAstudy
What side effects are normal after a dog's vaccine?
WSAVA describes these as commonly observed. Most settle on their own; your vet is the one to ask if you are unsure.
- Pain or a small swelling where the injection went in. WSAVAstudy
- Tiredness and sleeping more than usual for a short time. WSAVAstudy
- Eating less, or skipping a meal. WSAVAstudy
- A mild fever, which can make a dog feel warm and quiet. WSAVAstudy
- An episode of vomiting. WSAVAstudy
How common are vaccine reactions in dogs?
Uncommon, though WSAVA says they are underreported, so the true figure is hard to know.
38 per 10,000
dogs had a reaction of any kind within 3 days, in a US study of 1.2 million dogs Journal of the American Veterinary Medical Association (2005)study
62.7 per 10,000
dogs had a reaction in a Japanese study of 57,300 vaccinations WSAVAstudy
83.3 %
of reactions in the Japanese study were noticed within 12 hours WSAVAstudy
27 %
higher risk with each extra vaccine at one visit, for dogs of 10 kg or less Journal of the American Veterinary Medical Association (2005)study
Which dogs are more likely to react?
Size, breed and the number of vaccines given at once all matter. The Moore study of more than 1.2 million dogs found that the reaction rate fell as body weight rose, and that each additional vaccine at a visit raised the risk by 27% in dogs of 10 kg or less and by 12% in larger dogs. Young adult, small, neutered dogs given several vaccines at one visit had the highest risk. WSAVA adds that a later US study of nearly 5 million dogs found breed mattered on its own, with Dachshunds, Boston terriers, miniature Pinschers, French Bulldogs and Havanese at higher risk.
That is why the AAHA guidelines say reducing the number of vaccines given at one visit is a particularly useful approach in small dogs, with at least two weeks between visits. It is not a reason to ask for a smaller dose. WSAVA does not recommend giving small or tiny dogs less than a full dose, and AAHA says reducing the volume below the maker's recommendation is not advised. If your Shih Tzu, Pomeranian or Dachshund has reacted before, ask your vet whether to split the vaccines across visits.
Keep the risk in proportion. AAHA says licensed dog vaccines have a high degree of proven safety and efficacy, and that the benefits of vaccination far outweigh the risks, even for dogs with an unknown history.
What should you do on vaccine day?
Do
- Tell your vet if your dog is unwell on the day. AAHA says vaccinating a dog with an existing medical problem needs the owner's informed consent, because the risk can be higher. AAHA (JAAHA)study
- Tell the vet about any earlier reaction, and ask for each vaccine and its batch to be written on the card. WSAVA asks vets to record reactions so staff are alerted at future visits. WSAVAstudy
- Stay close to the clinic, or at home where you can watch your dog, for the first hour. Serious allergic reactions generally start within minutes to an hour. WSAVAstudy
- Ask your vet to report any suspected reaction to the vaccine maker. WSAVA says reports should be made even when a link is only suspected. WSAVAstudy
Don’t
- Insist on every vaccine at one visit for a small dog that has reacted before. AAHA says fewer vaccines per visit is a useful approach in small dogs. AAHA (JAAHA)study
- Give any human medicine for soreness or fever. Only your vet should decide whether a reaction needs treatment. WSAVAstudy
- Ask for a half dose for a small dog. WSAVA does not recommend it. WSAVAstudy
- Skip future vaccines on your own after a mild reaction. The vet weighs the risk and the protection your dog already has. WSAVAstudy
If my dog reacted once, can it be vaccinated again?
Often yes, but it is the vet's decision. WSAVA says a dog with a past serious reaction does not necessarily need to be revaccinated: if the vaccine thought to be responsible was a core modified live vaccine and the dog was vaccinated properly before, it is very likely to remain protected, and a blood test for antibodies can be considered. For rabies vaccines the local authorities must be consulted, because rabies certificates are often required by law.
If vaccination is needed, WSAVA says switching to a different product, or one with very low levels of the ingredients thought to cause allergic reactions, may help, and that a dog that has reacted should be watched closely for up to 24 hours afterwards. AAHA adds that a past reaction does not mean one will automatically recur, and that limiting the number of vaccines at each visit is prudent.
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Questions owners ask
Is it normal for a dog to be tired after a vaccine?
- Yes. WSAVA lists lethargy, a poor appetite, mild fever and pain at the injection site among the commonly seen reactions. Call your vet if your dog stays unwell, stops eating or seems to get worse, and go straight back for facial swelling, hives or collapse.
How soon after a vaccine can a reaction happen?
- Serious allergic reactions usually start within minutes to an hour. In a Japanese study reported by WSAVA, all cases of anaphylaxis began within 60 minutes and 83.3% of all reactions were noticed within 12 hours. Some other immune reactions can appear hours or even longer afterwards.
My puppy has a lump where it was vaccinated. Should I worry?
- Pain and swelling at the injection site are common local reactions, according to WSAVA, and they usually settle. Show your vet any lump that grows, is hot or very painful, or does not go down, so they can check it.
Are small dogs more likely to have vaccine reactions?
- Yes. In a US study of more than 1.2 million dogs, the reaction rate fell as body weight rose, and each extra vaccine at one visit raised the risk most in dogs of 10 kg or less. Vets may split vaccines across visits for small dogs, but WSAVA advises against reduced doses.
Can a vaccine give my dog the disease?
- WSAVA says the most common reason a young vaccinated puppy develops a disease such as parvovirus soon after vaccination is that it was already incubating the infection, or caught it while its mother's antibodies were still blocking the vaccine. Tell your vet straight away about any vomiting or bloody diarrhoea.
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Sources
Each source was opened and read on the date shown. How Petym checks its sources
- WSAVA: Core and non-core vaccines for pet dogs (opens in a new tab)
- WSAVA: 2024 guidelines for the vaccination of dogs and cats (WSAVA Vaccination Guidelines Group, Journal of Small Animal Practice) (opens in a new tab)
- AAHA (JAAHA): 2022 AAHA canine vaccination guidelines (opens in a new tab)
- Journal of the American Veterinary Medical Association (2005): Adverse events diagnosed within three days of vaccine administration in dogs (abstract read) (opens in a new tab)