December 2021

In this VETgirl online veterinary continuing education blog, Ellen M. Carozza, LVT reviews the latest “scoop” on feline vaccines. Should you be doing anything differently for your feline patients when it comes to vaccinology?

The Latest Scoop on Feline Vaccines

By Ellen M. Carozza LVT, AAFP/AAHA Feline Vaccine Guidelines Task Force Member

Vaccines are meant to help prevent disease, yet in practice many cats do not return in time for booster vaccines as kittens, let alone maintain a consistent vaccine history throughout their life. What can result is vaccine failure and poor immunity in our feline friends that can lead to the spread of disease and even death. The goal of the veterinary practice is to provide their clients with science-based evidence on what vaccinations are necessary to keep their cat(s) healthy and to prevent any outbreaks of disease in the pet populations seen in practice.

Recently, the American Association of Feline Practitioners (AAFP) and the American Animal Hospital Association (AAHA) have made necessary updates to the Feline Vaccine Guidelines (Source: 2020 AAHA/AAFP Feline Vaccination Guidelines. Journal of Feline Medicine and Surgery (2020) 22, 813–830) that reflect the cats we see in practice by defining their populations and breaking down what vaccines are necessary to keep these cats disease free. A key component of the guidelines are comprehensive, easy-to-reference tables listing approved core and non-core feline vaccines and the relevant considerations for their use. The guidelines are complemented by an online resource center at vaccination and supplemental materials at vaccinations. The online resources include frequently asked questions about vaccination that clinicians and pet owners raise as well as a vaccine protocol calculator that uses a cat’s life stage and lifestyle information to suggest an appropriate, individualized vaccination protocol.

Cats have been defined into five (5) populations, which included the additions of TNR (Trap-Neuter-Return/Trap-Neuter-Release) and foster cats, since the explosion of feline rescue and the public’s desire to help with care and control of these populations at the local level has increased. While these cat populations may not make up a high percentage of cats seen in your practice, they do need to be recognized as part of the cat populations that the public and the veterinary clinics they come into contact with for preventive care. Cattery cats, while formally defined as “cats that are maintained in commercial facilities; for example, breeding or boarding facilities, and pet stores with a showcase model,” can also include the popular “cat cafes” as those facilities tend to house a large number of cats that are under chronic stress. This makes them more susceptible to communicable disease as the number of cats directly affects the possibility of illness to occur.

PRO TIP: It is important that ALL homes with families that have permanent resident cats while also fostering cats for shelters and rescues be defined as a HIGH-RISK home. ALL permanent resident cats should be currently up to date on all necessary vaccinations with the proper immunity time given before any foster cats are allowed into the home.

Not only have cats been separated into populations, but lifestyle has been taken into consideration as well and a Lifestyle-based Calculator has been provided to allow easier breakdown for vaccination recommendations for the feline patient. One of the current recommendations that has changed for a particular life stage is the addition of FeLV for ALL kittens as a CORE vaccine regardless of lifestyle. Vaccine Risk-Benefit Assessments still play a major role for vaccination recommendations. The practitioner should be taking the following into consideration:

● Age and lifestyle
● Health Status
● Agent Exposure
● History
● Immunodeficiency

It is encouraged to create an individualized, Lifestyle-based vaccination plan for each cat. Questions must be asked about the lifestyle of that specific cat as well as any other cats in the household or potentially introduced into the household. Travel, boarding, housing, and enrichment activities or excursions outside of the home should also be considered. This risk assessment for exposure to disease should be done at least once a year. It’s important to note that a generic vaccination plan or protocol cannot be applied to every cat. Each cat must be evaluated individually and a plan formulated between the cat owner and their clinician for that particular cat. As with multi-cat households, the vaccination plan for the individual cat must be considered in relation to the entire population. An easily accessible chart has been made available for download that breaks down CORE and NON-CORE vaccine recommendations for pet cats and shelter cats due to the difference in risk category.

Core vaccines are for all cats with an unknown vaccination history. The targeted diseases cause significant morbidity and mortality and are widely distributed. In general, vaccination for core diseases results in good protection. The Task Force recommends the following vaccinations:

● Rabies
● FeLV (cats younger than 1 year of age)
● (FCV) feline calicivirus; (FHV-1) feline herpesvirus-1; (FPV) feline panleukopenia

The FVRCP series are recommended to be given at a 3–4-week interval starting no earlier than 6 weeks of age until 12-20 weeks of age with ADDITION of revaccination at 6 months* of age rather than at a year old to decrease the window of susceptibility if the kitten had MDA at the last kitten booster of (16-20 weeks of age.) Revaccinate every three (3) years thereafter.

Non-Core vaccinations are optional vaccines that should be considered in the light of exposure risk; that is, based on geographic distribution and the lifestyle of the cat. Optional or non-core vaccines for cats include FeLV (for cats older than 1 year), Chlamydia felis, and Bordetella bronchiseptica vaccines. The only vaccination that is currently not generally recommended for use is the FIP (intranasal-attenuated live) vaccine. This vaccine contains a serotype II strain of FIP virus. Serotype I FIP virus strains predominate in the field, and do not have cross-reactive neutralizing epitopes with serotype II strains. There is insufficient evidence that this vaccine induces clinically relevant protection in the field.

With the concerns of over vaccination by clients and the veterinary community, the question of serology testing before vaccination has been discussed and a chart providing a breakdown of the usefulness of the testing for the pathogens under fire has been created. The interpretation of an antibody test result can be complex because antibody testing is used for many reasons.
Depending on the antibodies tested for, antibody testing can be used for:

● Diagnosis of infection
● Identification of previous exposure to pathogens (particularly in unvaccinated animals
● Assessment of immunity prior to or following vaccination.

Clinicians should understand when and why they should perform antibody testing and use this knowledge to make evidence-based decisions prior to vaccination. Unfortunately, antibody testing is not reliable for assessment of immunity for FHV-1 and FCV as they both require an antibody and cell-mediated immune response. Test results should not be used to decide whether to vaccinate. Vaccination against rabies is essential in regions where it is required by statute/law or where the virus is endemic and should follow label recommendations. Serum neutralization results cannot be used to decide whether to vaccinate against rabies.

No vaccination is without the potential for an adverse response as each individual is unique in how it responds to foreign material being introduced for an immune response. The currently available feline vaccinations have an excellent safety record; however, the true prevalence of adverse reactions is likely to be underestimated owing to underreporting by both veterinarians and owners. It is important to document any adverse response in the pet’s personal medical records for future vaccine considerations regardless of severity. The vaccine manufacturers should be contacted. as well as consideration to report known or suspected adverse events directly to the Center for Veterinary Biologics of the U.S. Department of Agriculture’s Animal and Plant Health Inspection Services.

The most commonly reported vaccine reactions are lethargy, anorexia and fever for a few days after vaccination, or local inflammation at the site of injection, which is one of the reasons why it’s important to track the location where the vaccination is given as injection site sarcomas are of concern in the feline patient. While anaphylaxis is rare (it may manifest as vomiting, diarrhea, respiratory distress, facial or generalized pruritus, facial swelling, and collapse) it still can occur regardless of the cat receiving a previous vaccination for the pathogen. Where revaccination is considered necessary in a cat that has experienced an allergic reaction, using a different vaccine formulation and premedication with an antihistamine and glucocorticoid 20–30 minutes prior to vaccine administration is recommended, followed by close observation of the patient for several hours.

Currently, the Feline Vaccination Guidelines Task Force recommends that veterinarians and owners monitor the vaccination site for swelling or lumps using the “3-2-1” rule.
Biopsy of any mass present is warranted if it:

● Remains present 3 months after vaccination
● Is larger than 2 cm in diameter
● Increases in size 1 month after vaccination

It is recommended to obtain an incisional biopsy on any masses meeting any of these criteria. Fine-needle aspirates may not provide diagnostic cellular tissue, whereas excisional biopsies rarely meet appropriate margins (5 cm in two fascial planes) as required in the case of injection-site sarcomas, which increases the morbidity and mortality risks associated with sarcoma invasion. It is important to have follow up examinations and phone calls to check on any clients with pets experiencing an adverse response where a Feline injection site sarcoma (FISSs) is of concern.

Since FISSs are a risk, the Task Force recommends vaccination in the lower distal limbs to facilitate clean margins if surgical amputation is required. Other recommendations are as follows:

● No vaccination in the interscapular space
● No decrease in vaccine volume size
● No ventral abdomen subcutaneous injections due to the need to remove to fascial planes and 5cm margins. This requires aggressive tissue removal from the abdomen and abdominal cavity

Utilize the recommended vaccination site as seen in the diagram provided (tail and distal limb) and document any other vaccinations in the chart where given to track any adverse responses. It is currently recommended to administer the vaccines in the following manner in the feline patient:

● FVRCP given in RIGHT front limb
● Rabies given in the RIGHT hind limb
● FeLV given in the LEFT hind limb

It is recognized that practitioners may need to use medically appropriate discretion regarding the anatomical location of vaccinations given. It is strongly advised to keep complete, accurate records for site and route of vaccination.

Everyone in the veterinary practice plays a crucial role in ensuring our feline patients are kept properly vaccinated. The Centers for Disease Control (CDC) provides a useful resource and online training module, “You Call the Shots: Vaccine Storage and Handling ,” for staff training on vaccination. Practices are encouraged to have a designated person to be the primary vaccine coordinator for the facility. Always have a secondary person to serve as an alternate in the absence of the primary coordinator. Both coordinators should be fully trained in the routine and emergency policies and procedures.

The Veterinarian’s Role:
● Patient assessment, regardless of appointment type of current vaccine status
● Discussion of an individualized vaccination plan for the patient and then discussed and agreed upon in collaboration with the cat owner

In addition to the development of a vaccination protocol for the cat, the veterinarian should provide staff education on the following:
● Zoonotic disease prevention
● Separate administration sites
● Potential life-threatening adverse events(anaphylaxis) and minor events(swelling) following vaccination
● Vaccine reconstitution and handling (AAFP recommends use within 30 minutes of reconstitution)
● Sharps safety procedures and accidental sticks

Credentialed Veterinary Technicians or Veterinary Assistant Roles/Responsibilities:
● Vaccine coordinator
● Vaccine Storage and inventory management
● Implementing Feline Friendly handling techniques in the hospital to minimize stress during examinations and vaccine administration
● Client communication and follow up, including verbal and written instructions on potential adverse events after vaccine administration and disease prevention

Reception/Client-Service Personnel:
● Maintain patient files with vaccination information (date, serial number and exp date of vaccines given)
● Scheduling follow up appointments for booster and yearly vaccines in advance. It is strongly encouraged to forward book appointments to minimize the possibility of missing the recommended boosters, especially in vaccines that require a series for proper immunity to develop.
● Understand potential life threatening and minor adverse events that can occur following vaccine administration that require veterinary assistance

Believe it or not, pet owner clients are an essential member of the cat’s healthcare team. While they can be instrumental in helping improve healthcare for their cats, the Task Force recommends that vaccination be performed by a veterinarian. Vaccination is a medical procedure, and while vaccines are available through sources other than a veterinarian, they may not protect a cat against disease unless properly stored, handled, and administered.

It is recognized that many rescues/shelters are giving vaccinations themselves instead of a licensed veterinarian. It is strongly encouraged to have the discussion on vaccine storage/handling, as well as complete records (including injection site, serial number and expiration date) shared to help ensure the cats are receiving the current recommendations based on risk assessment and life-stye with these groups.

Educational material and supplemental resources are available to the public by AAHA and the AAFP. Talking points to all clients should include:

● Vaccines help protect against specific diseases
● A veterinarian is the best person to evaluate a cat’s individual vaccine needs.
Veterinarian-administered vaccines are particularly important with respect to Rabies. Rabies, while fatal, is preventable and in many US States it is against the law for anyone other than a licensed veterinarian to administer a Rabies vaccine. Rabies vaccination for the cat is required by law in many but not all states. Ontario is currently the only Canadian province that requires rabies vaccination of cats. Even when areas do not require it, rabies vaccination is STILL recommended (see CORE VACCINE above.)
● Severe vaccine reactions are rare, yet veterinarians should convey the risk-benefit analysis of any vaccination

Remember, the client and veterinary practice team have the same goal: to provide the best possible care for the pet.













12. 2020 AAHA/AAFP Feline Vaccination Guidelines. Journal of Feline Medicine and Surgery (2020) 22, 813–830.

  1. Thank you for the article. Boosting kitten vaccines at 6 months is new to me as well as including FeLV as a CORE vaccine.


  2. A lot of very handy links to sites where you can get all the information for the owner, and the team.

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