Cat Vaccination: How to Balance Risks and Benefits – Catster

Hi, I’m Dr. Karyn! Read my introduction to learn more about me and my five hilarious cats: Clutch, Cyril, Alex, Zelda, and Zazzles.

You might think that, as a veterinarian, I would have a pretty rigid stance on vaccinations, but just like you, I want to make sure that the choices I make are based on facts and science and are right for my cats and my situation.

In veterinary practice, our recommendations need to be in line with the manufacturer’s guidelines; it’s simply not practical to have a multitude of different options for a multitude of different scenarios. With that in mind, there are three messages I’d like all cat owners to take home:

1. Vaccination ABSOLUTELY saves lives.
2. The final say is up to you on how often and what types of vaccinations you give your cats (with the exception of rabies).
3. Vaccination decisions should be based on FACTS, not FEAR.

I am often asked, “Is vaccination safe?” and the honest answer is that introducing a foreign agent into the body to elicit an immune response is not 100% safe, but it is much safer than leaving your pet exposed to the risk of contracting deadly viruses. So you may want to know:

Should I vaccinate my cats? YES.

Do I strictly follow the manufacturer’s guidelines? Not completely.

Am I aware that I am taking a risk if I do not follow these guidelines? Yes, but I base my decision on the risk factors of my specific situation.

If you want to know what influences my decisions about vaccinating my cats, we need to get some basics out of the way. Trust me, you’ll walk away feeling much more confident in making the right choices for your cats with a little more knowledge under your belt.

How vaccination works – In short words

The practice of exposing humans, and later animals, to a small dose of an infectious agent to trigger an immune response dates back to at least the mid-15th century, perhaps earlier. When smallpox was busy wiping out hundreds of millions of people worldwide, a process called variolation emerged, in which a small amount of fluid from a smallpox lesion was injected into a healthy human. This was a risky procedure since the chances of developing a fulminant case of smallpox were extremely high, but it began to demonstrate that a small dose of the virus could create enough of an immune response to make the patient immune.

But it wasn’t until a man named Dr. Edward Jenner (honestly, you can’t go anywhere these days without hearing about a Jenner!) discovered that the same immune response could be achieved using cowpox, a related but much safer poxvirus.

How does it work?

When a virus enters the body, it triggers the immune system to release pathogen-fighting cells such as neutrophils, monocytes, and lymphocytes (T cells and B cells). After a while, the body begins to produce lymphocytes that are more specifically adapted to fighting viral particles, resulting in a faster and stronger attack.

If the virus is successfully killed, the bone marrow continues to produce cells that can target that particular virus, called memory B and T cells. These memory cells can last for months, a few years, or a lifetime, depending on the virus and the individual.

The problem with relying on our natural immune response to a virus is that it is a gamble. We only develop natural immunity if we survive, and we may end up with long-term or permanent health consequences from the infection.

And this is where vaccination comes in.

A vaccine uses an inactive version of the virus to “trick” the immune system into producing an immune response and creating memory cells, without actually causing the infection. This often causes the patient to feel unwell or show some mild symptoms of the virus, but this is simply a sign of the immune system’s response.

And here the issue becomes a little more technical.

To trigger a good enough response to the inactivated virus, most vaccines contain something called an adjuvant. This adjuvant is what actually activates the immune system, making sure it gets to the stage of producing memory cells, and it is the body’s response to this adjuvant that usually creates most of the side effects. But the more powerfully the body responds, the more likely it is to create a good supply of memory cells, so that the next time the body encounters the virus, it can fight it off quickly and effectively.

The Biggest Problem with Feline Vaccination

Just like humans, cats often experience various side effects from vaccination, including lethargy, fever, or swelling. This may be uncomfortable for a day or two, but it is an expected reaction. True vaccine adverse reactions, where the injection triggers an extreme allergic or systemic reaction, are very rare.

The worst potential side effect of vaccination in cats is something called injection site sarcoma, a type of malignant tumor that can form where a vaccine has been administered. This nasty tumor requires aggressive treatment, including surgical removal of the mass.

Feline vaccines are traditionally given in the scruff of the neck because there is a lot of loose skin, making it much easier to inject, as well as more comfortable and less stressful for the cat. But if an injection site sarcoma grows in this location, it is difficult, if not impossible, to completely remove the tumor because it often extends all the way up the spine.

To combat this, it has been recommended that cats be vaccinated on one limb, as this would allow amputation if necessary to completely remove the cancer. However, the further down the limb we go, the less loose skin there is and the more painful and stressful the injection becomes, so it can be a bit of a case of weighing the risks and benefits, as well as finding other ways to reduce the chance of this effect.

Studies have shown that the feline leukemia virus vaccine appears to have a higher risk of inducing sarcoma, probably because the virus itself attacks the bone marrow and immune system.

One way to reduce the risk is to give the leukemia vaccine every 3 years instead of annually.

One company has created a non-adjuvanted vaccine, in the hope that this will result in fewer severe side effects, but this vaccine does not provide as long-lasting protection as those that contain an adjuvant, so it would need to be given annually.

Risk/benefit analysis

This is where your decision making comes in. You need to be aware and honest about the types of risks your cats face and talk to your vet about how to ensure they stay protected.

Cats living in breeding colonies, shelters or outdoors, with a higher risk of interacting with other cats, should be vaccinated against leukemia virus according to the manufacturer’s recommendations.

For indoor cats, once they have received a full primary vaccination series, and I generally recommend they do the kitten series, plus one a year later, you may want to think about whether or not they need to continue with this particular vaccination. While viruses like feline influenza can be transmitted through the air and on surfaces, leukemia virus requires direct contact between cats.

If you choose not to vaccinate against the leukemia virus, it is essential to ensure that all new cats entering your household have completed the vaccination series or have been tested for the virus before coming into contact with your cat.

My cats are 100% indoor and are no longer vaccinated against leukemia virus – they have no risk of exposure. However, I vaccinate them against feline influenza viruses every three years.

You might ask yourself, Why take the risk of using the leukemia vaccine?

When a cat is infected with feline leukemia, there is a window of time where, if the virus is successfully eliminated, the cat will survive and have acquired natural immunity. Hurray!

BUT we don’t know exactly how long this immunity lasts, and if the virus isn’t eliminated within that time, the cat will develop feline leukemia, a debilitating disease that often leads to suffering and death.

Some statistics:

• Approximately 3% of cats in the United States and Canada are affected by feline leukemia.
• Feline leukemia is fatal in 80-90% of cases.
• The incidence of injection site sarcoma is between 1 in 1,000 and 1 in 30,000 (0.1 to 0.003%).

Are vaccines safe?

Of course, they are not completely safe: we are manipulating the immune system with an artificially altered version of a virus. Does that sound safe to you? But it is much safer than risking surviving the actual virus.

The fact is that if we put something into the body to cause a reaction, side effects are inevitable. If a drug or vaccine claims to have no side effects, it probably has no therapeutic effect either.

I hate the fact that we live in a world where big pharmaceutical companies profit from disease and I think we are right to do our own research and ask questions.

BUT just because big pharmaceutical companies make money from vaccines doesn’t mean vaccines are bad.

Is it really a disgrace that there are people making billions off of every viral outbreak? Absolutely! But that shouldn’t mean we stop protecting our pets.

Natural immunity may work, but only if the cat survives.