Why do cats die after vaccination?

If you’re like a lot of cat parents and you are about to get your baby cat vaccinated after adoption in line with the vet’s prescription.

You’ve probably wondered if your cat would also die after vaccination like some you heard about.

Maybe you’ve even wondered if the vaccination would have side effects on your baby feline. 

Truth is, there’s a lot of information floating around about cats dying after vaccination, some true, some false.

That’s why we rolled up our sleeves and uncovered all the latest articles.

What we discovered is that cats could have allergic reactions towards the vaccines which could be mild or severe.


Then you’ll be even more surprised when you discover the symptoms and how they could be treated to prevent your cat from dying.

Read on to understand properly and make tremendous use of this information.

Can A Cat Die From Vaccination?

A vaccination is a genetic modification of an organism that has antigens for a non-infectious disease.

After injection, the immune system produces antibodies against that particular pathogenic bacterium.

The vaccine’s goal is to stimulate the immune system into producing particular cells that will circulate throughout the body.

As a result, when the cat is exposed to the virus or bacterium in real life, the immune system is ready to combat it.

The immune system can sometimes overreact, resulting in an allergic reaction to immunizations in cats.

An allergic reaction’s symptoms might range from minor to severe, depending on the type of vaccination received.

Your cat’s immune system is critical for keeping her healthy by defending her body from infectious diseases.

One of the most essential activities of the immune system is the production of antibodies against parasites, germs, bacteria, and viruses.

Unfortunately, this complicated system is unable to produce specialized cells to combat every disease that enters the body, thus vaccines are used to assist the immune system in its preparation.

After receiving her immunizations, a cat may have a few minor adverse effects, such as local swelling or soreness at the injection site. This isn’t an allergic reaction, so do not worry.

If your cat develops more concerning symptoms such as hives, facial swelling, difficulty in breathing, or collapse it could indicate an adverse reaction to a vaccine.

At this point, care for the situation needs to come in, and your cat needs to be taken to the vet for an emergency to prevent the situation from worsening to death.

Why Did My Cat Die After Vaccination?

Cats may die after vaccinations because of an overactive immune system.

The normal occurrence is that the antigen in the vaccination stimulates the immune system of the cat, causing it to produce specialized antibodies against the virus, bacteria, or disease.

Some feline immune systems, on the other hand, are hypersensitive and overreact to the antigen.

This leads to a series of symptoms that may result in death if not properly attended to. 

Any sort of vaccine can cause a wide range of reactions in cats.

Because most owners expect or do not report mild symptoms following immunization, determining the number of cats who have reactions can be challenging.

From most to least common, the most common side effects of immunizations are overall low energy, mild temperature, local discomfort or swelling at vaccine site, vomiting, facial edema, and generalized itching (estimated to be between 3 and 50 cats per 10,000 immunized) (pruritus).

Rarely, uncommon adverse effects like respiratory problems, polyarthritis which manifests as lameness, or cancer formation at the site of immunization have been recorded.

Acute collapse or death has also been documented, with prevalence estimates ranging from 0.1 to 3 cats per 10,000.

Seeing litters of kittens die miserably from feline parvovirus or cats fade and die swiftly from leukemia symptoms is very heartbreaking.

Therefore, vaccines are required, despite the minor dangers.

Vaccine reactions usually happen between 30 minutes to 3 hours of inoculation, while uncommon reactions can happen up to 3 days later.

In general, cats should be treated right once if they show signs of respiratory distress, collapse, or excessive lethargy.

Anorexia for more than 36 hours or lethargy for more than 48 to 72 hours is an additional reason to seek medical help.

The vet must be informed at subsequent vaccination appointments if your pet exhibits minimal symptoms that you think do not require evaluation.

Pretreatment or a change in the type of vaccine provided might be used as preventative measures before the next vaccine is delivered.

Adjuvant vs. Non-adjuvant Vaccines: How do they affect your cat and which Should You Choose?

Many veterinarians and veterinary technicians will make recommendations for cats, and many of them, veterinarians and veterinary technicians will have strong opinions on which and what types of vaccines should be given to your cat, especially in light of what was once known as Vaccine Associated Sarcoma (VAS) in cats.

Because vets know now that many types of injections, not just vaccines, can cause tissue inflammation and have the potential to cause a sarcoma, which is a type of cancer, in the area where the injection was given due to chronic inflammatory changes, VAS is now referred to as FISS (Feline Injection Site Sarcoma).

Following the advice of a group of clever individuals, as well as an observation in Porter Pet Hospital, the specific or not-so-specific link between adjuvant vs. non-adjuvant vaccines causing FISS in cats is one of the industry’s major concerns and debates.  

An important notice! You must notify your vet if you notice a lump developing at the injection site. 

If the lump: 

  • Persists for 3 months or longer after injection 
  • Ever becomes larger than 2 cm in diameter or  
  • Continues to grow in size one month after injection or vaccine, 

The American Association of Feline Practitioners (AAFP) recommends that it be monitored at home and that a biopsy is taken and sent to a veterinary pathologist.

Early intervention is critical for the treatment and possible cure of FISS-related malignancy.

Because of the aggressive nature of this malignancy, surgery is the only therapeutic option, and late intervention may render treatment impossible.

Follow these instructions and notify your vet right away if any of the above stated happens. With this rare condition, waiting is not an option.

Symptoms That May Lead To Cat Death After Vaccination 

Some cats show allergic reactions to vaccines which can be minor, moderate, or severe, and can occur within a few hours of the inoculation.

Killed vaccines like the feline vaccines for rabies and leukemia virus are frequently accompanied by severe reactions.

The following are the symptoms ranging from mild to severe reactions

Mild Vaccine Reaction

  • Swelling, redness, or pain at the injection site
  • Temporary joint soreness 
  • Temporary lameness 
  • Fever
  • Loss of appetite 
  • Sneezing lasting roughly 4-7 days
  • Low activity levels 

Moderate Vaccine Reaction 

  • Fever
  • Redness
  • Swelling of the neck, eyes, and/or lips
  • Urticaria (hives) 
  • Pruritus (itchy skin)

Severe Vaccine Reaction

  • Pale mucous membranes
  • Cold extremities 
  • Decreased blood pressure 
  • Breathing difficulties 
  • Diarrhea
  • Vomiting 
  • Shock
  • Cardiac arrest 
  • Seizures
  • Collapse 
  • Death

Treatment To Prevent Cat Death From Vaccination

These symptoms, if noticed early enough, can be treated to prevent your feline from dying after vaccination. 

If your cat has a mild allergy, there is usually no need for treatment. Antihistamines will be attempted initially in the case of a more moderate allergy.

Should these fail to relieve your cat’s symptoms, your veterinarian will most likely prescribe steroids.  

Anti-inflammatory medicines, such as corticosteroids and antihistamines, can be used to treat mild to severe allergic reactions symptomatically.

Within a week, a cat with a mild or severe adverse reaction to immunizations should be back to normal. 

Moderate allergic reactions, on the other hand, can progress and become severe over time, therefore the cat will need to be followed up for as long as the allergic reaction lasts.

Cats that have had a severe allergic reaction to immunizations should be taken to a veterinary emergency clinic as soon as possible.

The doctor will start giving the cat life support, such as intravenous fluids and oxygen. The feline’s airways will be monitored at all times to ensure that they do not get closed.

Felines that have been stabilized are likely to survive anaphylaxis, but they will need to be hospitalized for a few days after the shock has passed before going home.

Your veterinarian may recommend chemotherapy or radiation therapy, as well as amputation of the affected leg, if your cat develops sarcoma.

It is possible to prevent your cat from having reactions that may lead to their death. Vaccinations are a crucial element of keeping your cat healthy in general.

If your pet has ever reacted to a vaccine, be careful to tell your veterinarian. Your veterinarian may advise you to forgo a certain immunization.

When many immunizations are administered at once to smaller cats, the chance of a vaccine reaction increases.

If your kitten is a petite or miniature breed, your vet may recommend receiving her immunizations spread out over many days rather than all at once.


Wag Walking: Allergic Reaction to Vaccines in Cats

Porter Pet Hospital: Vaccine Reactions and Risks