Cat Vaccinations – A to Z Guide

Cat owners, for example, always have to deal with the dilemma of whether the cat should be vaccinated or not. As a cat owner, is it really that important?

If so, which vaccines should be administered? How often should these vaccines be given? Is my kitten at the right age for vaccinations? Is vaccination required by law? Are there side effects? Are these vaccines more harmful than beneficial?

These and more will be answered in this article as we go along. But first things first – how do vaccines work?

syringe for an animal

Vaccinations – A Quick History

1796 was a year that saw thousands of deaths caused by smallpox. It was also during this year that country physician Edward Jenner observed that milkmaids have displayed immunity to the disease.

During this time, Jenner attributed the milkmaids’ exposures to cowpox as the reason for such immunity. While cowpox may cause a certain level of discomfort and illness to humans, the infection pales in comparison to the effects of smallpox, which, in most cases, results to death.

And so it was at this time that the idea to expose humans to smallpox’s distant relative – the cowpox, was born. Jenner introduced the cowpox virus to healthy humans by exposing such subjects to blisters as caused by cowpox.

This, in turn, led to the cowpox-exposed subjects to gain a certain level of immunity to smallpox. And so the concept of vaccination was born.

As the years passed, the world gained an understanding of the importance of vaccines. Not only have vaccines been beneficial to humans but to animals as well.

In general, not only are vaccines developed to protect animals and pets; it is also to protect us, humans. This is especially true in ensuring that zoonotic diseases – those diseases that can be transferred from animals to humans – do not spread.

This is, as you would probably assume by now, the main reason why rabies vaccinations are of utmost importance to pets and are required by law in many states.

Vaccines – How Does it Work?

Vaccines make the immune system think that the body is threatened by disease; pushing the body’s immune system into activating its own defense system to release antibodies that ward off the invading virus.

There are two types of vaccines. It can either be made of killed viruses, or it can also be made of the weakened ones (also called as modified live or MLV). Vaccines can be administered individually or as a group (also known as multivalent).

The ways by which individuals can be vaccinated may be through injections. There are also other ways like the intranasal vaccines which were recently developed.

These are vaccines which can be given through nasal sprays (the manner by which the vaccine is sprayed into the nose), which offers the same effects as the injection method. These are always recommended in areas where the method is available.

In the case of our pet cats, the first visit usually means “kitten shots”. These are shots that are administered to boost the cat’s immune system.

In previous decades, veterinarians would require cat owners for yearly boosters which usually happen during their annual cat checkup. Recent studies, however, have proven that it would be to the cat’s (and the owner’s) advantage if the yearly booster is scrapped – making it every three years instead of an annual shot.

It was in the late 90s when, because of a huge number of tumor cases growing on spots where certain vaccines were injected, the veterinary world has again been plagued with the side effects of vaccines.

It was then that the American Association of Feline Practitioners (AAFP), American Veterinary Medical Association (AVMA), American Animal Hospital Association (AAHA), and the Veterinary Cancer Society (VCS) formed the Vaccine-Associated Feline Sarcoma Task Force (VAFSTF).

The organization is composed of government representatives, veterinarians, researchers, and clinicians to look into the increasing number of these cases and their possible reasons. Their investigation has provided answers to pressing vaccine-related issues and has also resulted in the segregation of certain vaccines into two groups.

One group is considered as “core” or those that are highly recommended for each and every cat. The other group of vaccines is composed of those that are non-core which are optional in nature. We will discuss these two groups in detail shortly.

These vaccination guidelines are reviewed every year, with new findings and studies being discussed to the members of the AAFP; after which an update is published.

vet examining kitten

The Live Versus the Killed Vaccines

As earlier mentioned, there are two types of vaccines – the live and the killed vaccines. Almost all of the vaccines are available in both versions but it would be very helpful for you to discuss everything with your vet before deciding on which is good for your cat.

And while injecting MLVs (containing live but weakened viruses) is always the preferred route, there is still a matter of consideration that should be placed on your cat’s health history, hence, the need for a discussion with your vet.

To reiterate, MLVs (or the Modified Live Vaccines) are administered into the body to “fool” the immune system of an invasion of an outsider. This results in the system to create antibodies to fight off the unwanted.

The type is known to be more effective than any other. But as always true in everything; there is a downside to the MLV.

Cats, and all other pets or even humans that have compromised immune systems may suffer from what experts call as the vaccine-induced diseases from the MLV injection. This would then give your cat more harm than good.

Remember when we stressed about the need to discuss this first with your vet? These cases of cat health history could eventually help you and your vet to determine the kind of vaccine to be used.

A killed vaccine is another type of vaccine. Killed vaccines are those that contain pathogens, bacteria or virus particles that have been grown/cultured and eventually killed through the heat method or by using formaldehyde.

It is this type of vaccine that still needs a stimulator to irritate the immune system for the latter to create antibodies. The stimulant is called an adjuvant.

The killed vaccines are usually recommended for cats that have compromised immune systems. This type, however, also poses a number of risks.

One of these risks is that this type of vaccine may not be as effective as the MLV. It is therefore recommended that there is a frequent booster of the vaccine.

The second concern that has been raised is that the adjuvant is somehow blamed for the increase of vaccine-associated sarcoma (VAS) or vaccine site sarcoma (VSS) – a side effect that results to malignant and fatal cancer.

This is the reason why, while an adjuvant works well with humans, dogs, and other species of animals, this is not recommended for cats.

Although both types have its pros and cons, it would be very beneficial for your cat if these options are discussed with your vet prior to the vaccination.

Core and Non-Core: What Are They?

Findings published by the AAFP in relation to the investigation of the increasing number of tumors in the vaccinated area have resulted in the classification of vaccines into the core and non-core groups.

Core vaccines are usually for diseases that are either very common, extremely severe in nature or diseases that could pose as a threat to humans.

The non-core vaccines, on the other hand, are given to cats that are considered to be highly at risk. This could be because of the cat’s lifestyle or the environment the cat is in.

As recommended, kittens should be given the core vaccines for as easy as six weeks of age. The vaccines for feline panleukopenia, feline rhinotracheitis, and feline calicivirus can also be administered as a group and is available as just one vaccine shot.

For these three, the vaccination is advised to be repeated at intervals of every 3 or 4 weeks until your kitten is 16 weeks old. The next booster shot for these diseases would be a year later.

For the rabies vaccines, it is a different story. Some vaccines against rabies can be given at 8 weeks of age; some at 12 weeks of age, with a booster shot after a year.

If you already have an adult cat, you need to discuss the intervals of vaccinations with your vet. As mentioned earlier in this article, some vaccinations would require a booster shot after a year while some would be required after three years.

This depends on the brand and the type of vaccines used. Discuss with your vet before deciding.

As suggested by AAFP, here are the diseases your cats should be vaccinated against:

The Core Vaccines

  • Feline Panleukopenia

Decades ago, it would have been impossible to think of a way out of feline panleukopenia (FP). The disease also comes in different names – feline distemper or feline parvo.

It used to have one of the highest mortality rates in cats. Lucky enough for the cats of today, vaccines that fight against this virus are available.

FP is a viral disease in cats caused by the feline parvovirus. It infects and kills cells that quickly grow and multiply like those that can be found in the bone marrow, developing fetus, and intestines.

While it can affect adult cats, the kittens are the most vulnerable.

So how do cats get infected? According to the experts, the virus exists in almost any kind of environment.

Infected cats shed the virus in their nasal secretions, urine, and even stool. Unvaccinated cats that come in contact with the virus get infected through these that the infected cat has shed.

It is thus advised that beddings, cages, dishes, and even the hands of the people who got in contact with the infected cat be completely cleaned to avoid the spread of the virus.

While some vets recommend yearly booster shots to fight feline distemper, some have already succumbed to the idea of a booster shot every three years. Kittens should be receiving the vaccine at age six to eight weeks as they are especially vulnerable to the virus.

  • Feline Calicivirus

This highly-communicable infection usually victimizes unvaccinated cats and is very common in cat facilities and shelters. The infection affects the cat’s respiratory system, from the nasal passages and the lungs, to the mouth, the intestines and the musculoskeletal system.

Ulceration of the tongue is also very common in infected cats. They can be infected by the virus when they are exposed to another infected cat.

The disease as being highly-contagious is reason enough why veterinarians recommend vaccination against the calicivirus.

  • Feline Viral Rhinotracheitis (FVR)

The infection attacks the respiratory system of cats. It usually affects the nose and the throat of your feline friends – the virus of which is caused by a healthy cat’s exposure to infected ones. The disease is possibly caused by any or all of the following – feline viral rhinopneumonitis (FVR), rhinotracheitis virus, and the feline herpesvirus type 1 (FHV-1).

The virus can be transmitted through saliva, eye and nasal secretions, or can also be spread via fomites. Fomites are objects that can possibly carry an infection. Examples are clothes, utensils, and the likes.

Recent developments have already resulted in the availability of one vaccine that can cover all three diseases. Shots can be done for kittens six weeks old with regular follow-up shots every 3 to 4 weeks until the kitten’s 16th week; after which the next booster is 12 months after the last shot.

  • Rabies

The rabies virus attacks the brain and the spinal cord of mammals. This virus that infects dogs, cats, and even humans is the cause of thousands of deaths worldwide.

This could possibly be the reason why when one utters the word “rabies”, people immediately squirm in fear as infection can almost always result in fatalities of the infected.

The rabies virus can be transmitted through a bite from an infected animal. Once in a while, it can also be transferred through the saliva when it enters another mammal’s body through an open wound.

In the US alone, rabies is most common in cats than in any other animal. Cats, or any pet for that matter, can be of high risk to be infected when they are in an environment where there are a significant number of unvaccinated cats and dogs or wild animals like bats, skunks, and foxes.

And the worst thing about the virus is that when an animal is infected, it does not immediately show any sign of the infection. While some can display symptoms a few days after exposure, some could take months before signs show up.

Symptoms include a change in behavior including aggression and restlessness. In some cases, there is also the loss of appetite, seizures, disorientation or even death.

The virus is so deadly as well as easy to transmit which is the reason why most states require pets to be vaccinated against rabies from an early stage. But how often do cats need rabies shots?

While some vaccines require a yearly booster shot, recent studies have already proven that some types of rabies vaccines for cats require boosts after every three years.

Non-Core Vaccines

  • Feline Leukemia

One of the non-core vaccines is for the disease feline leukemia. As the name itself suggests, the virus results in anemia or lymphoma.

In addition to these two, the virus also causes the suppression of your cat’s immune system and could make your cat vulnerable to other diseases.

The virus can be transmitted from one cat to another through saliva, blood, feces, and urine. It also does not live long enough outside a cat’s body and can only live for a few hours.

And because the immune system strengthens over time, kittens are more vulnerable than adult cats. What could give your cat the virus, however, is its exposure to infected cats.

Mostly, cats that stay indoors all the time are considered as low-risk compared to those that are always on the run. This is also the reason why the vaccine is deemed optional and is dependent on the cat’s environment and lifestyle.

  • Feline AIDS

This virus is also known as the FIV or the Feline Immunodeficiency Virus. The disease is also popularly known as the Feline AIDS.

Just like AIDS in humans, infected cats have a compromised immune system and are susceptible to diseases. Extra steps need to be taken for those that are found to be positive for FIV.

Feline AIDS is commonly transmitted through deep bite wounds. The wounds that are usually caused by cat fights outdoors are very common examples of how feline AIDS is transmitted from cat to cat.

This is the reason why most cat owners would prefer to have their cats stay indoors than be outside regularly getting into fights with other cats.

Another way by which the virus can be transmitted is from a mother cat to her kitten. This mode of transmission is something the kitten has no control over. Poor kitty!

Vaccines for FIV have been approved for sale in the market since 2002. But depending on the lifestyle of your cat, the vaccine may or may not be needed. Discuss this with your vet before you decide.

  • Chlamydiosis

While cat owners and vets all have the cat’s best intentions in mind, there are certain cases when a Chlamydia vaccine harms more than benefits. Some cats suffer from adverse reactions due to the vaccines.

And for the reasons that the vaccine can only prevent severe symptoms and not the infection itself, this vaccine is not usually recommended.

If you believe your cat is at risk for the disease, talk to your vet first. If your vet gives you the go signal, take note that re-vaccination should happen every year.

  • Feline Infectious Peritonitis (FIP)

This is one of the feared diseases among cats. The virus infects the white blood cells; the cells which transports the virus all over the cat’s system.

This results in an intense inflammation of the area where these viruses have been transported to; usually the abdomen, kidney, or the brain. The disease is caused by a strain called the feline coronavirus. But as the disease affects only a small percentage of cats, most vets do not recommend the vaccination.

  • Bordetella

This is normally found in dogs (kennel cough) but can also infect cats. Although the vaccine’s approval for sale is fairly new as compared to other vaccines, there is not much evidence as to its protection’s duration.

This is thus reason enough why vets do not necessarily recommend the vaccine amongst cats.

female vet giving vaccine to a kitten

Duration of Immunity (DoI)

In an abstract published by the National Center for Biotechnology Information, it was stated that core vaccines provide longer protection to cats more than non-core vaccines.

Take for example the vaccine for the feline calicivirus. According to the publication, this vaccine is effective for a minimum of three years.

And so whether your booster shot is after three years or after just one year, the level of protection to your cat is almost the same. This is also the same for other core vaccines for cats.

So what shots do cats need yearly? Non-core cat vaccines can only provide a certain level of protection for less than or equal to a year from the date of vaccination.

And so in cases when your cat has been vaccinated with a non-core vaccine, a yearly booster shot is necessary to maintain the same amount of protection.


As we now know, vaccines are quite helpful in ensuring that your cats do not easily succumb to any disease. This is the reason why giving them to your feline friends is a must, most especially the core vaccines.

This is so true except:

  • When your cat suffers from a chronic disease. Examples of such diseases are hyperthyroidism, chronic renal failure, a weakened immune system, or even asthma. Discuss the possibilities with your vet before the vaccination as there are ways to vaccinate cats with these conditions.
  • When your cat is more than 10 years old. Another term for these cats is “geriatric”. Geriatric cats need no boosters but can be tested for titers when going for their annual exams. This is usually to check the amount of antibodies that are in the cat’s system to determine the manner by which your geriatric cat is protected.
  • When your kitten is less than six weeks old. It should be remembered that kittens can only be vaccinated as soon as they reach their sixth week from birth, except when the kitten has been orphaned or lives in high-risk areas. Although this may not be absolutely true for all cats, it is also believed by some vets that certain vaccines can also cause stillbirths in pregnant cats.

Vaccine-Related Sarcoma (VAS): What is it?

Over the years, much information has been amassed on the topic of vaccine-related sarcoma that can be found in cats. Usually, the incident would occur as a result of FeLV vaccines.

While there are cases of VAS recorded as a result of rabies vaccines, those that are primarily due to FeLV vaccines far outnumber their rabies counterparts.

Some experts believe that there is a possibility of this being a result of the use of aluminum in certain vaccines. One such expert is Dr. Greg Ogilvie who discussed such a possibility during a lecture conducted about vaccine-induced fibrosarcomas in cats.

Because of the increasing number of incidents, the Vaccine-Associated Feline Sarcoma Task Force was created in the late 90s with the aim to study the problem – its scope, possible causes, and eventually its treatment. The findings on these studies can be found on the group’s website.

FeLV and VAS

As we now know, healthy cats get infected through saliva and nasal secretions. This can also be because of sharing food dishes, biting, or any other close contact with an infected cat.

This is also true for the feline leukemia virus.

As this puts all cats at risk of getting the virus, it is recommended that cats should be tested for this disease at least once or each and every time a healthy cat gets close to one that is known to be infected.

Cats that are new to the household should also be tested before it is allowed to mingle with other cats. And when one is found to be positive, the cat should be separated from the others.

The vaccine that fights against feline leukemia is popular for causing VAS in cats. And because feline leukemia is, in itself, deadly, it prompted the need for the FeLV vaccines to still remain in the market.

This is despite the risk it can possibly pose to cats. As such, some special recommendations have been put in place to ensure the safety of your cats.

The vaccine may not be considered as a core vaccine – meaning it is not required by vets and is deemed optional. It is, however, very helpful if you discuss possibilities with your vet to determine whether there is a need for such vaccination or not.

And if indeed there is a need, the vaccines should be given every year. And because of its risk in causing VAS to cats, there are special vaccination site guidelines that should be followed when administering FeLV (and rabies) vaccines.

  • Rabies vaccines – right rear leg
  • FeLV – left rear leg
  • Panleukopenia, feline herpes virus I, feline calicivirus – right shoulder

Now, you may be wondering why there is a need for vaccinations to be administered to such body parts. This is because when a VAS tumor grows out of the injected site – the leg, for example – vets can easily go for the amputation of the infected leg.

This would still allow cats to survive. If it is a leg that is amputated, cats can easily adapt to the amputation and can live as normal a life as possible with just three legs.

Imagine injecting the vaccine in the neck area. When a tumor grows in the neck, you just cannot amputate the head and expect the cat to survive. The example may be morbid but we hope it sends the message across.

Because of such fears of VAS, most cat owners resort to skipping the FeLV vaccine altogether. Optional as it is, it is still important to give the vaccine to your cat whenever needed.

The disease is as deadly as it can be. It would be unfair for the cat if you skip the vaccination because of such fear.

According to most vets, the FeLV vaccine is about 75% – 85% effective. Most cat owners would ignore the numbers and would resort to simply hoping their cats do not get infected with feline leukemia.

But as the disease is easily transmissible especially to cats that are always outdoors, we believe there is a need for such vaccinations. But if you, as a cat parent, believe otherwise, just at least have your feline friend regularly tested.

If you have an indoor cat, at least you have more confidence that your furry pal does not get infected. But if you still decide on the vaccination despite your cat being an indoor cat, talk to your vet.

Multivalent: The 3 in 1 Vaccine

Since the very beginning, vaccines have been developed to ward off a specific virus from entering the body. Over the years, however, scientists were able to come up with just one vaccine that can fight off numerous diseases.

In the case of multivalent cat vaccines, one shot contains agents that can protect your cat from feline calicivirus, herpes virus, and feline panleukopenia (FRCP).

Multivalent cat vaccines are like hitting three diseases with one shot. It is also interesting to note that these feline vaccines belong to the core vaccines – all of which, as previously discussed, are required by vets for your cat.

Recent studies have also led to the development of a vaccine that adds Chlamydia to the list. Of course, as the Chlamydia vaccine is part of the non-core group, you can discuss this first with your vet.

Despite the growing popularity of the multivalent vaccines for cats, it has always been met with controversies. Discussions are as heated as to whether a cat should be vaccinated or not.

With the emergence of multivalent vaccines, some pet owners have this firm belief that it poses the same amount of hazards to cats as that of an adjuvant; a claim some others disagree with.

While the debate on multivalent vaccines and their supposed risks and benefits are being heatedly debated on, experts and organizations like the VAFSTF and AAFP have not revealed any stand that could either disprove or confirm these claims. This makes it harder for cat owners to decide on the welfare of their own cats in relation to multivalent vaccines.

Should Your Cat Be Vaccinated?

We all want the best for our cats. We all aim for our cats to live healthy, normal, and long lives.

And so before deciding for or against a certain vaccination, please do your research. This article may give you the A to Z of cat vaccinations but this was written with hopes that it could stimulate you to discover as much as you can find.

In short, as in all cases, there would always be the pros and cons that you should discuss with your vet. Each cat is different as much as one vaccine brand varies from the other.

An understanding of your cat’s health, needs, and reactions to vaccines would enable you and your vet to decide on which vaccines your cat should be given. It would also be enough bases for you to determine how often these vaccines are to be administered.

Remember that while some cat vaccines require booster shots after a year, there would be some that require re-vaccination after three years.

It should also be emphasized that every cat environment is different. Your decision as to the matter of cat vaccinations should be made after a thorough discussion with the vet.

Remember to research on the subject and decide through that, rather than base your decisions on what your neighbor said about this and that.

If, for example, you and your vet have already decided to go for or against a certain cat vaccine, just commit for your cat to still get its annual physical checkup to ensure it leads a healthy and long cat-life. Because at the end of the day, all nine cat lives can be used up if we, cat parents, disregard preventive measures like the vaccines.

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