Do Cats React to Vaccinations?

Vaccinations are necessary for most cats, especially those that spend most of their time outdoors. Although the experience is unpleasant, you should vaccinate your cats against some diseases.

All vaccinations can cause side effects in cats. Fever, lethargy, decreased appetite, and swelling are not uncommon. Some cats may also have difficulty walking and experience stomach upset. However, these adverse side effects should subside after 24 to 48 hours.

Vaccinating a cat always carries a risk. However, this risk alone is not enough to avoid cat vaccination. In most cases, the benefits far outweigh the risks.

However, it would be best to make an informed judgment about whether to vaccinate your cat. This is best done based on available medical data.

What Types of Vaccinations Are Available for Cats?

Your veterinarian offers essential vaccinations for your cat. These primarily protect against the following diseases:

  • Feline rhinotracheitis (cat cold)
  • Feline herpes virus (FHV-1)
  • Feline calicivirus (FCV)
  • Combination of these three vaccinations into one (FVCRP vaccine)
  • Rabies
  • Feline panleukopenia
  • Feline leukemia virus (FeLV)
  • Feline immunodeficiency virus (FIV)
  • Feline infectious peritonitis (FIP)
  • Bordetella
  • Chlamydophila felis

None of these vaccinations for cats is required by law. However, they are still beneficial.

If you want to travel abroad with your cat, however, there are some countries where certain vaccinations are mandatory. For example, rabies vaccination is required by law in most states in the United States.

But even if vaccination is not required by law, it is still advisable. Many diseases are transmissible among animals and also to humans.

How Are Vaccines Given to Cats?

Cat vaccines are usually administered by injection, usually into the legs.

In the past, many veterinarians also gave the shots in the neck. This was because of the flexibility of the skin in this area. It is easier to pull the skin and apply a shot.

In recent years, the risk of feline injection site-associated sarcoma (FISS) has become more prevalent. This indicates that the neck area should always be avoided.

FISS can cause a tumor at the injection site. This tumor would need to be removed, which is not easy in the neck.

A rabies vaccine is usually given in the right hind leg, while a vaccine against FVCRP is given in the right front leg.

Not all vaccines need to be injected. Bordetella, FVCRP, and FIP vaccines can be inhaled nasally. However, the nasal vaccines may not be as effective as injections.

If your cat receives the vaccinations intranasally, she will sneeze and sniffle for a while afterward. She may also have watering from her eyes and nose.

What Are the Most Common Side Effects of Cat Vaccinations?

The cat’s immune system will begin to adjust after a vaccination, which means the cat may feel sick.

However, this is only a concern if she does not recover quickly. Some common side effects of cat vaccinations are:

  • Fever
  • Lethargy
  • Low energy
  • Loss of appetite
  • Vomiting and diarrhea
  • Swelling at the injection site
  • Difficulty walking
  • Strange behavior
  • personality changes

These side effects should be of short duration. If your cat is still uncomfortable 48 hours after vaccination, ask your veterinarian for advice.


Because the vaccine is injected into the cat’s leg, you can expect temporarily limited mobility. There may be some swelling at the injection site, making it difficult for your cat to move.

The FVCRP vaccine will most likely cause limping, as lameness is a symptom of feline calicivirus.

However, lameness syndrome in cats is a temporary problem. Cats that struggle with this side effect recover as quickly as they get the problem.

Cats vaccinated against the virus sometimes suffer temporarily from stiffened joints. This, of course, makes them passive.

Any movement is painful throughout this side effect. Your veterinarian can prescribe a pain reliever suitable for cats.

Vomiting and Diarrhea

After vaccinations, you should watch for vomiting in your cat.

A cat’s body adjusts after a vaccine is administered. This can upset your cat’s stomach.

Diarrhea is also possible for the same reasons.

Low Energy

It is natural for a cat to become listless and sleepy after a vaccination.

A cat will want to be alone for a few hours after vaccination to rest. She may also develop a high fever.

Make sure your cat is left alone. Tell any children in the house not to disturb your cat.

Lack of Appetite

Loss of appetite is a common side effect of vaccinations.

If a cat has not eaten for 24 hours, it is a cause for concern. Cats lack fat reserves to feed them.

Watch to see if your cat eats, is reluctant, or refuses to go to its bowl.

Walking to the bowl may feel like a long trip if your cat has little energy or is limping. This is especially true for older cats with joint problems or arthritis.

Lumps at the Vaccination Site

The most concerning reaction to vaccination is Feline Injection Site Associated Sarcoma (FISS). This is a cancerous tumor that develops after inflammation at the injection site.

Your veterinarian must examine a cat with a lump if it persists weeks after vaccination.

Another sign of FISS is a lump larger than 1 inch (2 cm) in diameter, especially if it continues to grow.

If the sarcoma caused by vaccination is not treated, it will continue to grow. This, in turn, allows the cancer cells to spread. Soon, the lungs and other internal organs will be affected.

It is not entirely clear why cats get FISS. Some experts believe that the cats already have tumors. The inflammation caused by the vaccine activates the malignant tumor and causes it to spread.

If you present your cat with FISS to a veterinarian, surgery will be needed to remove the tumor. Your cat may also need to undergo radiation or chemotherapy.

FISS remains rare, with an incidence of only about 1 in 10,000.

Can Cats Be Allergic to Vaccines?

A cat can be allergic to a vaccine. Cats can be allergic to anything. They might even react to your veterinarian’s rubber gloves when administering the vaccine.

An allergic reaction is more problematic than a typical reaction to a vaccine. Signs that your cat has an allergic reaction to the vaccine include:

  • Outbreak of wheals on the skin
  • Swelling around the face, eyes, mouth, and throat
  • Breathing problems
  • Sharp drops in body temperature on the paws and tail
  • Low blood pressure and decreased heart rate
  • Seizures and collapse

These reactions are treated with steroids or antihistamines to reduce the effects of the allergy.

Your cat may need intravenous fluids and further observation in more severe cases.

Personality Changes in Cats After Vaccination

Some cats temporarily behave differently after vaccination. In a few cases, they are never quite the same. This is rare, but it does happen.

The reason is that the vaccine triggers a chemical reaction in the cat’s brain. However, this reaction usually only lasts about 48 hours.

If your cat seems to have undergone a complete personality change, you should contact your veterinarian. Make a note of any changes in your cat’s behavior.

What Side Effects Can Vaccinations Have for Older Cats?

Older cats have weaker immune systems than young cats. Therefore, they are more susceptible to disease. On the other hand, they are more affected by side effects.

If your senior cat has a chronic disease, you should avoid vaccinations. These treatments can worsen problems with the heart and kidneys.

Assuming her health has not worsened recently, there is no reason to deny her booter shorts if your cat has tolerated vaccinations well in the past.

However, having your cat vaccinated in general is advisable if she spends a lot of time outdoors.

Respiratory diseases that certain vaccines protect against can be fatal to older cats.

Cats can react badly to vaccines, an inevitable side effect of the procedure. These reactions should not be severe.

In most cases, the risks of vaccination are outweighed by the safety that vaccines provide.

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I, Daniel Popovic (Place of residence: Germany), process personal data to operate this website only to the extent technically necessary. All details in my privacy policy.
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I, Daniel Popovic (Place of residence: Germany), process personal data to operate this website only to the extent technically necessary. All details in my privacy policy.