How many times have you received a reminder that your dog or cat is "due" for vaccines? I appreciate reminders. We all need a little help remembering when routine veterinary care like an annual exam is due. But when it comes to vaccines, I don't believe a calendar should be the only thing making the decision.
Vaccines have a place in veterinary medicine; however, their overuse and misuse have become increasingly evident. They have been proven effective for some infectious diseases, but not all vaccines are the same, they are not without risk, and not every pet requires the same protocol.
Our pets are individuals. A hunting dog living on a farm has a very different lifestyle and exposure risk than a dog living in a city apartment. An indoor-only cat has a different risk profile than a cat who spends time outdoors. A young puppy has different needs than a senior dog with a long vaccination history.
When it comes to vaccination, I believe we should look at the individual animal rather than simply following a one-size-fits-all schedule. This is where titer testing can be incredibly useful. A titer can help us determine whether a pet has antibodies to certain diseases and, for some important core vaccines, whether those antibody levels are associated with protection.
Instead of automatically giving another vaccine because a certain amount of time has passed, we can ask more useful questions: “What is my pet’s risk level?” "Is my pet still protected?" “Is it required by law or optional?”
What Is a Titer?
A titer, pronounced "tight-er," is a blood test that measures antibodies against a particular infectious disease. When a dog or cat receives a vaccine, the vaccine stimulates the immune system to recognize a specific virus or other pathogen. The immune system responds by developing defenses against that pathogen, including antibodies. A titer measures those antibodies in the blood.
Laboratory titers are typically performed by repeatedly diluting a serum sample and determining how far the sample can be diluted while antibodies still demonstrate the activity being tested. The final dilution at which that activity can still be detected is called the endpoint, and that is what produces the titer value.
In simple terms, a titer gives us information about whether antibodies are present and, depending on the test, how much antibody activity can be detected. But there is an important distinction: A titer measures antibodies. It does not measure every part of the immune system. We'll come back to that because it is one of the most important limitations of titer testing.
Vaccination and Immunity Are Not Exactly the Same Thing
This is another important distinction. Vaccination means administering a vaccine. Immunization means the animal's immune system has responded to the vaccine in a way that provides protection. Most healthy animals develop an immune response following appropriate vaccination. But individual responses can vary. Some animals may not develop adequate immunity after vaccination. Others may maintain protective antibodies for years. That's one reason I like the idea of titer testing.
Rather than assuming that every animal has responded exactly the same way—or that every animal has lost immunity simply because three years have passed—we can run a titer. A titer can tell us whether antibodies are currently detectable. For certain core vaccines, those antibodies are strongly associated with protection.
Why Consider Titer Testing?
There are several reasons I may recommend considering a titer.
1. To Avoid Unnecessary Revaccination
This is probably the reason pet parents hear about titers most often. If an adult dog or cat already has protective antibodies to a core vaccine, giving another dose may not provide additional benefit.
The University of Wisconsin's CAVIDS laboratory describes titer testing as a scientifically supported way to assess immunity to certain core vaccine agents. Their laboratory notes that an already immune pet would not be expected to benefit from another dose of the vaccine virus, while there is at least some risk of an adverse reaction. I don't believe we should vaccinate simply because we can. We should vaccinate when there is a reason to do so.
2. To Determine Whether a Pet Responded to Vaccination
Titer testing can also work in the opposite direction. Sometimes we assume a pet is protected because the pet was vaccinated. But vaccination does not guarantee that an individual animal developed immunity. This is particularly important in puppies and kittens.
Young animals receive antibodies from their mothers through colostrum. These maternal antibodies provide valuable early protection, but they can also interfere with vaccination. If maternal antibodies are still present when a modified-live vaccine is administered, they may neutralize the vaccine before the puppy or kitten can develop its own immune response.
This is one reason puppies and kittens optimally should wait to receive vaccinations if in a closed, safe environment where there is minimal exposure, until they are roughly 12 to 16 weeks of age. A titer after the initial series can help determine whether the animal actually developed antibodies to certain core vaccine viruses, typically done 4 weeks after vaccination. In other words, a titer isn't only about avoiding vaccines. It can also tell us when a pet may need a vaccine.
3. For Pets With a History of Vaccine Reactions
This is another situation where I think titers deserve serious consideration. If a dog or cat has experienced a significant reaction after vaccination, I don't want to automatically expose that animal to another vaccine without first asking some questions.
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What vaccine was given?
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What type of reaction occurred?
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How severe was it?
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Does the pet still have evidence of immunity?
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Is the vaccine actually necessary for this particular animal?
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Could a titer provide useful information?
Kansas State University's Veterinary Diagnostic Laboratory specifically lists checking vaccine titers as one consideration for pets with previous adverse vaccine reactions, along with reassessing lifestyle and vaccine needs. Every case is different, but a previous vaccine reaction is a good reason to have a thoughtful conversation with your veterinarian before giving another dose.
Which Vaccines Can Be Evaluated With Titers?
Titers are not useful for every vaccine. For a titer to be meaningful, we need to know that the antibody measurement correlates with protection from disease. For certain core viral vaccines, that relationship has been established through research and challenge studies.
In dogs, useful core vaccine titers include:
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Canine Distemper Virus
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Canine Parvovirus
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Canine Adenovirus Type 2
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Infectious Canine Hepatitis
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Rabies Virus
In cats:
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Feline Panleukopenia Virus
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Rabies Virus
These are the diseases for which veterinary diagnostic laboratories have established antibody thresholds associated with protection.
The University of Wisconsin CAVIDS laboratory performs quantitative testing for these viruses and explains that protective thresholds have been established through laboratory research and challenge studies.
What About FVRCP in Cats?
FVRCP is the combination vaccine commonly used to protect cats against:
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Feline rhinotracheitis/herpesvirus
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Calicivirus
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Panleukopenia
Titers can be particularly useful for feline panleukopenia, because antibody levels correlate well with protection. The situation is more complicated for feline herpesvirus and calicivirus. For some viruses, antibodies do not prevent infection altogether, and a particular antibody level cannot reliably tell us whether an animal will become infected or develop disease.
This is an important concept: The ability to measure an antibody does not automatically mean that the antibody measurement tells us whether the animal is protected. The test needs to have a meaningful relationship to protection.
What About Lifestyle Vaccines?
This is where titer testing becomes much less useful.
Vaccines such as:
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Bordetella
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Lyme disease
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Leptospirosis
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Canine influenza
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Feline leukemia virus
are generally considered based on the individual pet's risk of exposure and lifestyle.
For many of these diseases, there is no established antibody level that can reliably tell us that a pet is protected. For example, the University of Wisconsin notes that protective antibody thresholds are not established for several non-core vaccines, including Lyme, leptospirosis, Bordetella, and influenza.
That means a titer isn't necessarily going to answer the question: "Does my pet need this vaccine?" For these vaccines, the more important question may be: "Does my pet have enough exposure risk to warrant this vaccine?" That is where lifestyle comes in.
How Does Titer Testing Work?
The process is relatively simple. Your veterinarian draws a small amount of blood from your dog or cat. The blood is processed to separate the serum, which is then submitted to a veterinary diagnostic laboratory. The laboratory tests the serum for antibodies against the specific pathogen or pathogens requested. The result may be reported as:
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A quantitative numerical titer
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A positive or negative antibody result
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An interpretation such as antibody being present at or above a particular laboratory threshold
Some veterinary clinics use in-house screening tests that provide a quick positive or negative result. These can be useful, but they are not technically the same as a quantitative laboratory titer. A quantitative laboratory titer determines an endpoint by progressively diluting the serum and determining the last dilution at which the antibody still demonstrates the activity being measured.
If you're considering testing, ask your veterinarian: "Is this an in-clinic antibody screening test or a quantitative laboratory titer?" Both can have a place, but they provide somewhat different information.
What Does a Protective Titer Mean?
This is an area where the terminology can become confusing. For some core vaccine viruses, researchers have established antibody thresholds associated with protection. If your pet's antibody level is at or above that threshold, it provides strong evidence that the pet is protected against that particular virus.
The University of Wisconsin laboratory explains that these thresholds have been established through challenge studies in which animals with particular antibody levels were exposed to the infectious virus. This is important because we don't want to assume that any detectable antibody automatically equals protection. The level, disease, testing method, and the laboratory’s established threshold matters.
What If the Titer Is Negative?
This is where things get more complicated. A negative titer means that the laboratory did not detect antibodies at the level or with the method used by that particular test. For some core vaccines, a negative result suggests that the animal may benefit from vaccination.
The University of Wisconsin laboratory, for example, states that a pet with no detectable antibody is highly likely to benefit from a dose of the appropriate vaccine. But there is an important limitation that we need to understand. Antibodies are not the entire immune system.
Titers Cannot Measure Memory Cells
This is probably the most important limitation of titer testing. Vaccination can create immunological memory. The immune system has memory B cells and T cells that can remain after circulating antibody levels decline. These cells can help the immune system respond more quickly if it encounters the pathogen again. A standard titer does not measure those memory cells. We don't have a simple blood test that we can routinely run in your veterinarian's office and say: "Your dog has enough memory cells, so we know exactly how protected he is." Unfortunately, it isn't that simple.
This means that the absence of detectable circulating antibodies does not necessarily prove that an animal has no immune memory. At the same time, we cannot simply assume that an animal is protected because it was vaccinated years ago if there is no measurable antibody and no other way to assess immunity. This is one reason why a titer result should always be interpreted in the context of the individual pet.
A Titer Is One Piece of the Immune Puzzle
I like titer testing because it gives us information and can help prevent over vaccination in certain cases. But I don't want anyone to think that a titer is a perfect measurement of immunity because it isn't. A titer does not tell us:
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How many memory B or T cells your pet has
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How long the current antibody level will remain
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Whether the immune system will respond perfectly to every exposure
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Every aspect of cell-mediated immunity
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Every component of innate immunity
It also doesn't guarantee that a pet can never become infected. For certain core viruses, however, the relationship between antibody levels and protection is strong enough that titers can provide valuable clinical information.
What If the Titer Is Detectable but Low?
This is another situation that requires interpretation. A pet may have detectable antibodies but not reach the laboratory's established threshold for sterile immunity. That doesn't necessarily mean the animal has zero protection. The University of Wisconsin laboratory notes that detectable antibodies below the sterile-immunity threshold may reduce the severity of disease even though it may not completely prevent infection.
If a result falls into this gray area, your veterinarian may consider:
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The pet's age
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Overall health
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Previous vaccination history
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Lifestyle
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Risk of exposure
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Previous vaccine reactions
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The specific disease
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The laboratory's interpretation of the result
This is why I don't recommend looking at a titer number without understanding what that number actually means.
What About Rabies Titers?
Rabies is a special situation. Rabies antibody testing is available, but a rabies titer generally does not replace a legally required rabies vaccination. Rabies vaccination requirements are determined by state and local law. So if your pet has a measurable rabies antibody level, don't assume that you can legally skip a required rabies vaccination.
If your pet has had a significant reaction to a rabies vaccine, talk with your veterinarian about the options available where you live. Medical exemptions may be available in some jurisdictions, but the rules vary. Rabies is also a serious zoonotic disease, which is one reason it is treated differently from many other vaccines.
When Should You Consider Titer Testing?
There isn't one schedule that is right for every animal.
Titer testing may be worth discussing when:
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Your adult pet is being told it is time for another core vaccine. Instead of automatically vaccinating, ask whether a titer can provide useful information first.
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Your pet has a history of vaccine reactions. A titer may help determine whether another dose is necessary.
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You want to confirm immunity after puppy or kitten vaccines. This can help identify whether the animals developed an adequate antibody response.
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Your pet has an uncertain vaccination history. A titer may sometimes provide useful information about existing immunity.
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Your pet is older and has received many vaccines. This is another situation in which it may be reasonable to ask whether another booster is actually necessary.
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You are trying to make an individualized vaccination plan. Lifestyle, health, previous vaccination, and titer results can all contribute to the conversation.
How Often Should Titers Be Checked?
There is not a single answer that applies to every pet. The University of Wisconsin CAVIDS laboratory states that a three-year interval is appropriate for many adult dogs and cats when quantitative tests are used, while puppy testing may be useful after the initial series and again around one year of age. However, the appropriate interval depends on the individual pet and the reason for testing.
Your veterinarian may recommend a different approach based on:
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Your pet's age
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Health status
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Previous vaccination history
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Previous titer results
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Exposure risk
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Type of test being used
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Specific disease being evaluated
I don't think we should turn titer testing into another rigid schedule. The point of testing is to get useful information that can help guide an individual decision.
Where Can You Get Titer Testing?
If your veterinarian doesn't offer titer testing in the clinic, you may still be able to have your pet's sample sent to a veterinary diagnostic laboratory.
Your veterinarian can collect the blood sample, separate the serum, and submit it according to the laboratory's requirements.
University of Wisconsin–Madison CAVIDS Laboratory
The University of Wisconsin–Madison CAVIDS laboratory offers quantitative antibody testing for:
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Canine distemper
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Canine parvovirus
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Canine adenovirus
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Feline panleukopenia
The laboratory provides instructions for serum collection and submission.
University of Wisconsin–Madison CAVIDS Titer Testing
Kansas State Veterinary Diagnostic Laboratory
Kansas State Veterinary Diagnostic Laboratory offers vaccine titer testing for dogs and cats and provides information about interpreting titers and their role in vaccination decisions. Submissions are only accepted from a veterinarian.
Kansas State Veterinary Diagnostic Laboratory – Dog and Cat Vaccine Titer Testing
Texas A&M Veterinary Medical Diagnostic Laboratory
Texas A&M Veterinary Medical Diagnostic Laboratory offers vaccine antibody testing for several canine and feline vaccine antigens. The laboratory explains which tests are available and the limitations of interpreting antibody results for different vaccines.
Texas A&M Veterinary Medical Diagnostic Laboratory – Vaccine Titer Testing
More Resources
The Healthy Dog Workshop offers laboratory titer testing utilizing the Kansas State Veterinary Diagnostic Laboratory.
Nayked Pet offers laboratory titer testing with 2 consultations.
Affordable Pet Labs offers titer testing in select areas.
Always check with the laboratory for current pricing, available tests, sample requirements, and submission instructions.
Questions to Ask Your Veterinarian
If your dog or cat is due for vaccines, I encourage you to have a conversation rather than simply saying yes or no. You can start with:
"Can we check a titer before giving another core vaccine?"
Then ask:
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Which vaccines are you recommending?
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Which of these are core vaccines?
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Which are lifestyle or risk-based vaccines?
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Does a titer correlate with protection for this particular disease?
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Is the test quantitative or a positive/negative screening test?
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What laboratory will perform the test?
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What does a positive result mean?
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What does a negative result mean?
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What happens if the result is borderline?
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Does my pet's previous vaccine history affect your recommendation?
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Does my pet's lifestyle increase exposure risk?
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Is this vaccine required by law?
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Does my pet have a history that makes avoiding unnecessary vaccination particularly important?
These questions can turn a routine vaccine appointment into a much more individualized conversation.
Titer Testing Doesn't Mean "Never Vaccinate"
I am against automatically vaccinating without considering whether the individual animal actually needs another dose. Over vaccination is a real issue in veterinary medicine.
Core vaccines have a role in protecting dogs and cats from disease. The goal is to use vaccines appropriately. That means considering the disease, the vaccine, the pet's lifestyle, the pet's health, previous vaccination history, and—when appropriate—titer results.
The Bottom Line
Titer testing gives us another tool for making informed vaccination decisions. For certain core vaccines, including canine distemper, canine parvovirus, canine adenovirus, infectious canine hepatitis, rabies virus and feline panleukopenia, antibody levels can provide valuable information about protection. A positive, protective titer may tell us that an additional vaccine is unlikely to provide meaningful benefit at that time. A negative or low titer may tell us that the pet could benefit from additional vaccination. And sometimes the result simply tells us that we need more information and a thoughtful discussion about the individual animal.
The important thing to remember is that titer testing is not a perfect measurement of immunity. It measures circulating antibodies, not memory cells or every other component of the immune system.
When used for the right diseases and interpreted correctly, titers can give us information that we would not have if we simply looked at the calendar. I don't believe every dog and cat should automatically receive every available vaccine or on the same schedule.
We need to find the middle ground: protect pets from disease while avoiding unnecessary vaccination. That means looking at the individual animal. Look at lifestyle, risk, health history, and previous vaccine responses. When a titer can give us useful information, use the information to make an informed decision. Our pets are individuals. Their healthcare should be individualized, too.
Additional resources:
https://healthydogworkshop.com/the-trouble-with-titers/
https://www.avma.org/javma-news/2016-07-01/titer-or-revaccinate
https://www.vetmed.wisc.edu/lab/cavids/frequently-asked-questions/
https://ksvdl.org/laboratories/rabies-laboratory/dog-cat-vaccines-titer-testing.html
https://tvmdl.tamu.edu/education-library/vaccine-titer-testing/
https://titersforpets.org/about-titers/
Disclaimer: This content is for informational purposes only and is not meant to diagnose, treat, or replace consulting a primary veterinarian for individualized care.