Feline Leukemia Virus (FeLV) in Cats: Why Early Vaccination Matters

Kittens often look perfectly healthy—bright-eyed, curious, and full of energy.

But some of the most serious threats to their health aren’t visible at all.

Feline leukemia virus (FeLV) is one of those diseases.

At PetMed of Key West Veterinary Clinic in Dubuque, we consider FeLV vaccination an essential part of kitten care—because once a cat is infected, there is no cure.

What Is Feline Leukemia Virus (FeLV)?

FeLV is a contagious virus that affects a cat’s immune system.

Over time, it can lead to:

• Chronic infections
• Weight loss
• Anemia
• Certain cancers, including lymphoma

It is one of the leading infectious causes of death in cats.

One of the most challenging aspects of FeLV is that infected cats may appear completely normal for months—or even longer—before showing signs of illness.

How FeLV Spreads

FeLV spreads through close contact between cats.

This includes:

• Mutual grooming
• Shared food and water bowls
• Bite wounds
• Saliva exchange

It does not survive long in the environment, but it spreads very efficiently between cats that interact.

Many cats who carry FeLV show no obvious symptoms, which means exposure can happen without anyone realizing it.

Why Every Kitten Should Be Vaccinated 

At PetMed of Key West, we recommend the FeLV vaccine for every kitten.

Even if a cat is intended to be indoor-only, early protection is important.

Why?

Because kittens:

• Are more susceptible to infection
• Have developing immune systems
• Are more likely to have unpredictable exposure early in life

And just as importantly:

Cats are excellent escape artists.

Doors get left open. Screens fail. Curious kittens explore.

What starts as “strictly indoor” doesn’t always stay that way.

That’s why we focus on protecting them early—before exposure ever happens.

When We Reassess Risk

After the first year of life, we take a more individualized approach.

Around 1–2 years of age, we reassess each cat’s lifestyle:

• Strictly indoor, stable household → vaccine may no longer be needed
• Indoor/outdoor or exposure to other cats → continue yearly vaccination
• Homes that foster, adopt, or bring in new cats → continued protection strongly recommended

This allows us to balance protection with each cat’s real-world risk.

Cats at Highest Risk

We strongly recommend ongoing FeLV vaccination for:

• Indoor/outdoor cats
• Cats that roam or spend time outside
• Cats exposed to other cats of unknown status
• Households that bring in stray or rescue cats
• Multi-cat households with changing populations

In these situations, exposure risk is significantly higher.

The Importance of Testing

Vaccination and testing go hand in hand with FeLV.

Before introducing a new cat into the home—or if there has been potential exposure—we recommend testing for FeLV.

This helps:

• Identify infected cats early
• Prevent spread to other cats
• Guide long-term care decisions

Because once FeLV is introduced into a household, it can quietly spread if not identified.

The Vaccine Schedule

• Initial series: Two doses given 3–4 weeks apart, starting around 8–9 weeks of age
• First booster: One year later
• Long-term: Based on lifestyle and risk

Our Approach to the FeLV Vaccine

At PetMed of Key West Veterinary Clinic, we use the Boehringer Ingelheim PureVax® feline leukemia vaccine.

We specifically choose this vaccine because of its safety profile in cats, as it is designed to reduce the risk of injection-site reactions that have historically been a concern with some feline vaccines.

Our goal is to provide strong protection while also prioritizing long-term safety for every feline patient.

A Preventable Disease with Serious Consequences

We’ve had to make this diagnosis too many times:

A young cat with:

• Unexplained weight loss
• Recurring illness
• Or cancer

And behind it is FeLV.

Once a cat becomes infected, there is no cure.
We can manage symptoms—but we cannot eliminate the virus.

That’s why prevention matters so much.

The Bottom Line

FeLV is a serious, life-altering disease.

But it is also preventable.

Vaccinating early gives kittens protection during their most vulnerable stage of life.

After that, we can reassess and tailor care to fit each individual cat.

Protect early.
Reevaluate later.
And give your cat the best chance at a long, healthy life.

FeLV Vaccine FAQs

Do indoor cats really need the FeLV vaccine?

We recommend it for all kittens. After the first year, we reassess based on lifestyle.

How is FeLV spread?

Through close contact with infected cats, especially saliva (grooming, shared bowls, bites).

Can FeLV be cured?

No. Treatment is supportive, but the virus cannot be eliminated once a cat is infected.

Should new cats be tested?

Yes. Any new cat entering a household should be tested before introduction.

How often does my cat need the FeLV vaccine?

All kittens receive the initial series and first booster. After that, it depends on risk.

Local Care You Can Trust

PetMed of Key West Veterinary Clinic proudly serves Dubuque, Asbury, Peosta, Epworth, Dyersville, Farley, and surrounding communities.

If you’ve recently brought home a kitten or are unsure about your cat’s FeLV status, we’re here to help you build a plan that fits your cat’s life.

Written by Dr. Mackenzie Hellert

Updated 3/30/26