side effects after vaccinations: Black chihuahua on coach

Occasionally puppies may yelp a little when a vaccine is given.

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Side effects after vaccination: Vomiting and diarrhoea in dogs

By Dr. Laura Waring BVetMed MRCVS Veterinarian

Updated on the

Why vaccinations are important for keeping your dog healthy – and how your pet reacting badly to them is extremely rare.

Vaccinations are an important part of ensuring your dog remains healthy. Modern vaccinations are safe and effective, and ensure your dog is protected from deadly diseases. Vaccinations are started when your dog is a puppy, typically around eight weeks of age (but the vet can advise on this) and then annually after that.

In the most cases, vaccinations do not cause a problem for your puppy or dog. Yet very occasionally in a small percentage of dogs, vaccines can cause side effects, or incredibly rarely a more serious allergic reaction. But the risk of these is far outweighed by the benefit of the protection the vaccine gives.

What are the side effects of dog vaccinations?

Vaccinations like any medication can occasionally cause side effects. Yet in the majority of dogs there will be no noticeable side effects, and in a small minority there may be some very mild symptoms. Very, very rarely some animals might have an allergic reaction to a vaccination. But the small risk of side effects is far outweighed by the protection the vaccination gives against potentially deadly diseases. If you think that your dog might be experiencing a vaccination reaction, contact the vet, and do this urgently if you pet seems very unwell.

Common side effects might include a slight fever, lethargy, reduced appetite and slight swelling around the injection site (this usually resolves within two to six weeks). These are the most common side effects.

Rare side effects include vomiting, diarrhoea, itchy skin, swelling of the face or around the eyes. If you notice any of these side effects, you should seek urgent veterinary care for your dog.

How long after a vaccine can a reaction occur in dogs?

Most mild side effects will occur in the 48 hours after a vaccination is given and be very short-lived, lasting just a few days. If your dog has a rare allergic reaction to a vaccine, this usually occurs within a few minutes or up to an hour after a vaccine is given.

Can Lyme vaccine make a dog sick?

The Lyme disease vaccination is not part of the core vaccination programme in the UK. The vaccine itself does have a higher risk of side effects than other vaccinations routinely used. Therefore its use must be weighed up on a risk-benefit analysis with a veterinary surgeon, if you live in an area where your dog may encounter Lyme disease frequently. It may be better to ensure that tick control is used to protect your dog (as ticks transmit the disease). By treating your dog with an effective tick product that kills the ticks quickly, disease transmission will not occur.

What should I do if my puppy or dog vomits after vaccines?

If you notice your puppy or adult dog is vomiting or has any other type of digestive upset after having vaccinations, then contact the vet right away. It is possible the dog is having a reaction to the vaccination. Dogs are routinely vaccinated against canine parvovirus, distemper, adenovirus and leptospirosis, and it is possible that dogs can have a reaction to any of the components.

Will my puppy be sick after vaccination and deworming?

It is common for dogs to be prescribed worming or flea treatments during their visit to the vets for a check up and inoculation. It is possible that these treatments can also cause digestive upsets or other reactions in your dog or puppy. As such, if possible, delay giving these for a couple of days after the vaccination so that if there is a problem you know what has caused it.

What can I expect at my dog’s vaccination?

Most visits for your puppy or dog's vaccination will be straight forward and routine. The vet will check over your pet before administering the vaccine. Because a small needle is used, most dogs won’t react or find the procedure painful. But occasionally puppies may yelp a little as the vaccine is given or just after it is given.

Will my puppy have side effects after vaccination? 

Puppies can occasionally experience vaccination side effects in the same way that adult dogs can. Most commonly the puppy may be slightly quieter following the vaccination or may sleep a little more. A slight temperature may also be experienced. Don't worry if your puppy is slightly off their food for a day or so. The more serious side effects or allergic reactions such as hives, vomiting or swelling can also occur, and if your puppy has these symptoms, contact the vet straight away.

Should my puppy be yelping after vaccination?

When the vaccination is actually administered, some puppies will make a small yelp. If they seem to be uncomfortable or vocalising a lot at home following a vaccination, seek advice from the veterinary surgeon.

Will my dog's behaviour change after vaccinations?

In the vast majority of cases there will be no side effects experienced when your dog has their vaccinations. This is because modern vaccinations are safe and effective, and in which case you can carry on as normal with day-to-day activities and exercise. Having said that, a small minority of pets might experience a mild reaction. They might be feeling tired or experience a slight temperature, and may need to rest for a couple of days. If your pet is lethargic, their behaviour may be slightly different to usual, and they will be less interested in playing.

What can I give my dog for pain after shots?

If you feel that your dog is in pain or not well following vaccination, please contact a vet for advice. If your pet is experiencing mild symptoms of a reaction, such as lethargy or a slight temperature, then quiet rest at home is likely to be all that is needed. Ensure your pet has a comfy bed and access to plenty of fresh water, offer food as usual and keep a close eye on them. If their condition worsens, contact the vet.

Why is my dog lethargic after their shots?

Lethargy following vaccination is one of the most common mild side effects that some dogs experience. It should be slight, and only last for a couple of days. You might also notice your pet has a reduced appetite. If the lethargy seems extreme or your pet isn’t drinking, seek advice from a vet. Otherwise, if all seems to be otherwise well, allow your pet to rest and avoid exercise.

When should I see a vet?

In the majority of cases a dog will not have any problems after vaccination, and therefore there is a huge benefit to avoiding them becoming unwell with the diseases that the vaccination protects against. Occasionally mild side effects, such as lethargy or a mild temperature, might be experienced. If your dog is experiencing anything more than this, such as digestive upset, any evidence of pain or swelling or itchy skin, then advice should be sought from a vet. You know your pet best and, if you are concerned there is a problem following your dog or puppy's vaccination, don't hesitate to seek advice get them checked by the vet.

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