What Is FIV and Why Is the FIV Vaccine No Longer Available?

Natalie Stilwell, DVM, MS, PhD
By Natalie Stilwell, DVM, MS, PhD on Jun. 21, 2019

If you have cats, you may have heard of feline immunodeficiency virus (FIV). FIV is a retrovirus (similar to HIV) that is transmitted directly from cat to cat through close contact—usually through bite wounds and scratches.

FIV is most commonly diagnosed in outdoor cats, and once a cat is diagnosed as FIV-positive, they remain infected for life. It seems logical that you would just need to get an FIV vaccine to protect your cat, but the vaccine is no longer used. Why is that?

Here’s what you need to know about FIV, the FIV vaccine, why the vaccine was discontinued, and how you can safeguard your feline family members against infection.

Why Was the FIV Vaccine Discontinued?

From 2002 until 2017, the FIV vaccination was available in the United States and Canada. It was generally considered safe, with rare and usually minor side effects.

But the vaccine has since been discontinued, and many pet parents want to know why it was taken off the market.

Here are the four main reasons why cats no longer get the FIV vaccine.

Indoor Cats Weren’t Usually at Risk

The FIV vaccine for cats was considered a noncore vaccine, which means it was administered on a case-by-case basis—depending on an individual cat’s risk of infection.

FIV is transmitted through saliva; therefore, cats that are in close contact with each other (through fighting) have the highest risk of getting infected. The most at-risk cats include outdoor or stray cats, especially intact adult males, who are more likely to roam and fight for territory and food.

Indoor cats generally have a very low risk of getting FIV and rarely received the FIV vaccine. So even when it was available, not many cats actually received the vaccine.

The FIV Vaccine Offered Limited Protection

The vaccine contained certain strains of inactivated virus, which offered protection against some (but not all) FIV infections.

In other words, vaccinated cats that were exposed to any of the strains not included in the vaccine were at full risk of getting infected. This was particularly an issue in certain geographic areas, like the United Kingdom, where the vaccine offered little-to-no protection.

Frequent Boosters Increased the Risk of Sarcoma

In addition to offering limited protection, the vaccine also needed to be readministered on a yearly basis. But the FIV vaccine was an adjuvanted vaccine, which means that it contained additives that stimulate the immune system.

This raised concerns of vaccine-site sarcoma, a type of cancer that can develop at the injection site when a vaccine contains adjuvant.

The Vaccine Led to False-Positive FIV Results

Another issue with the FIV vaccine was that vaccinated cats could test positive for FIV for up to four years after vaccination. These false-positive results occurred because tests could not distinguish antibodies produced by the vaccine from natural infection.

Therefore, vaccinated cats were at risk of being incorrectly diagnosed with FIV. This wasn’t a big deal if a cat’s vaccine record was known, but if the cat ended up in a shelter, it could lead to euthanasia.

In response to this, it was widely recommended that vaccinated cats be permanently identified (for example, microchipped) and wear a collar at all times to avoid being mistaken as FIV-positive in a shelter.

Alternatives to the FIV Vaccination

Prevention is the key to avoiding FIV infection. So, even though the FIV vaccine is no longer on the market, there are several steps that you can take to safeguard your cat against the disease.

Spaying and neutering is recommended for all cats. This will help reduce fighting behavior and, therefore, the risk of infection. Also, keeping your cats indoors will minimize their risk of encountering FIV-positive cats, who tend to live outdoors and are often strays.

Also, any new cats in your household should be tested for FIV so that you can determine the risk of disease transmission to other cats in the home.

You might think that cats living with FIV-positive cats would definitely become infected, but recent studies have shown that FIV transmission in multi-cat households is actually rare.

FIV is not likely to spread through normal contact (such as mutual grooming) or by sharing food and water bowls.

What If Your Cat Is Already Infected With FIV?

While infected cats may maintain a relatively normal lifestyle and life expectancy, the virus can eventually impair the immune system and cause progressively worsening health issues.

Cats suffering from advanced stages of FIV may experience fever, weight loss and recurrent infections throughout the body.

But many FIV-positive cats can lead normal lives if they are well-cared for, monitored for infections and taken for regular vet checkups.

Featured Image: iStock.com/ajr_images

Related Video: Which Vaccines Does My Pet Need?

Natalie Stilwell, DVM, MS, PhD


Natalie Stilwell, DVM, MS, PhD


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