Vaccination Reactions in Cats
Although Anaphylaxis is considered to be rare once it begins it is extremely dangerous

Vaccination reactions in cats are most often associated with sarcomas, but these tumors are just one of the possible reactions.

Adverse reactions to vaccinations have been studied for several years in humans, but they can also occur in your cat.

The age of your cat as well as the type of vaccine that is used play major roles in a reaction, but it is widely held that the benefits far outweigh the potential risks.

Although it is still considered for a vaccination reaction to be uncommon, it will be anything but uncommon if it affects your cat.

For this reason, it is very helpful for an owner to understand the possible risks.


Green eyes in catsThere are precautions you can take against Vaccination reactions in cats

Vaccination reactions in cats start with what is referred to as Anaphylaxis, which is a relatively rare but extremely dangerous condition.

In fact, if it does occur and is not treated immediately, it can rapidly take the life of your cat.

Anaphylaxis is an allergic reaction to something that your cat has ingested, or in this case, to something injected.

This reaction will occur very quickly in your cat, but there is some misconception on the time frame.

It can occur within just a matter of minutes in some cases, but it can also take as long as twenty four hours for it to appear.

If it does take several hours, it is much more dangerous.

The reason for this is that if it does occur within minutes after a vaccination, your cat is still at your veterinarian and they can react very quickly.

However, if it takes several hours and you are not totally aware of what is happening, you may not have time to get professional help.

Anaphylaxis can cause shock, respiratory failure, as well as cardiac failure in your cat. If it is severe enough, it can also cause a sudden death.

However, it is estimated by the medical community that only one case in every 15,000 vaccinations results in Anaphylaxis, but this is just that; an estimate, as there are no exact numbers.

This form of vaccination reactions in cats is almost always associated with what is referred to as a killed vaccine, and the two most common are Rabies and Leukemia vaccinations.

The reason for this is that a killed vaccine has a lot more virus or bacterial particles per dosage, as well as chemicals that are added and designed to help your cat’s immune system.

However, all of these combined can also increase the chances of your cat having an allergic reaction.

If your cat is about to have either of these types of vaccinations, there are several possible symptoms that you should watch for very closely.

If you see any of them, you will need to react as quickly as possible.

The first symptom will be a very sudden onset of diarrhea or vomiting that will happen so fast your cat will not make it to their litter box.

If this does occur, check their gums as well as their limbs immediately. If their gums are pale and their limbs are cold, it is an extreme emergency.

By now, your cat’s heart rate will be extremely rapid but their pulse will be so low you may not be able to detect it.

If your cat is not treated as soon as possible, you will begin to see the next symptoms; shock that is followed by a seizure. Sadly, this may also result in the death of your cat.


Vaccination reactions in cats next possible threat is perhaps the best known; sarcomas.

A fibrosarcoma in your cat is a tumor of their connective tissues that have a tendency to go very deep into their skin.

In recent years, this form of tumors has dramatically increased and there is a lot of speculation in the medical community that they may be the result of vaccinations, especially the FeLV vaccine.

Since this is either strongly recommended or required in some parts of the world, it has led to an entire re-evaluation of the process as well as new sets of protocols.

It is this sudden growth of fibrosarcoma that has prompted the medical community to now recommend that adult cats that have very limited exposure to FeLV not be vaccinated.

However, if your cat has had this vaccination, there are several things that you can watch for. The first is a very small swelling that will start to appear at or near the site of the vaccination.

There will be no pain associated with this in most cases, so your cat will not notice it and chances are, you will also miss it unless you are looking for it.

It is not uncommon for a slight bump to appear with all vaccinations, and these are not considered to be vaccination reactions in cats as they will usually go away in a few weeks.

But if they do not, look even closer. If it does persist for more than three months and starts to grow, something is definitely not right and the chances are now very high that it is this form of vaccination reactions in cats.

These tumors are considered not only very dangerous, but also very invasive as they go very deep into your cat tissues.

They can be surgically removed, but this will also require removing a lot of healthy tissue surrounding the tumor as well.

In the vast majority of cases, they will also require radiation as well as chemotherapy treatments.


Vaccination reactions in cats do not stop there, as there are several other potential reactions. The next list includes neurological diseases, especially cerebellar diseases.

These types of diseases are much more common in kittens that are less than five weeks old when vaccinated and include Ataxia, which is a failure of motor coordination, as well as Dysmetria.

Dysmetria is a situation where your cat cannot regulate the rate, the range, as well as the force of any type of movement.

It will result in what is called high stepping as your cat cannot judge any type of distance.

These types of reactions are almost always associated with what is referred to as modified live vaccines.

The next possible set of vaccination reactions in cats may be discomfort at the injection site as well as fevers.

However, these are not considered to be anywhere as dangerous as the other possible reactions.

If the swelling is normal, it will be cause pain, redness, as well as irritation to your cat, and this can easily occur within a few hours or days after the vaccination.

In most cases, they will gradually go away, but if they do not, you need to have your cat examined.

Fevers are also common within a few days after the vaccination, but this should also resolve itself on its own. Fevers are most common with Chlamydia vaccinations.

Lameness is another of the possible vaccination reactions in cats, and can be caused by several different vaccinations including the modified live calicivirus vaccine.

This symptom can occur within a few days or a few weeks and can easily be treated with fluids and antibiotics and will generally not become a long term problem.


There are some steps you can take against vaccination reactions in cats. The first form of protection is to use cold compresses as soon as your cat is vaccinated.

You should use ice packs or other forms of cold compresses for at least two to three hours directly after an injection.

Compress the area for 30 minutes and then allow time for their skin to breathe; than repeat the process.

There are other methods of protection, especially if your cat has any type of an immune compromised condition.

Once you know when your cat will be vaccinated, start these well in advance.

They include supplements of both Omega 3 as well as Omega 9 fatty acids, but avoid Omega 6 in this case only.

You can also use Echinacea drops which are natural immunity boosters, but the key to both is to give them at least two to three weeks in advance to help booster your cat’s immune system,


Vaccination reactions in cats are considered to still be rare, but they will be anything but rare once they occur in your cat.

Understanding what they are and how to recognize and react to them, may save your cats life.

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