Manual on Cat Vaccines and Vaccination Process

Most content of this article is based on the Dog and Cat Vaccination Guidelines published by UC Davis Veterinary Hospital in January 2018 and the 2013 AAFP Cat Vaccination Test Report and the 2010 Vaccination Guidelines prepared by the WSAVA VGG Group.This article is a mere pile of personal opinions; each cat has a different health condition and living environment, and the specific vaccinations should be determined according to the cat. This article is a mere pile of personal opinions; each cat has a different health condition and living environment, and the specific vaccinations should be determined by the cat. Any questions should be directed to your veterinarian first.


Why vaccine counts?

Vaccinations play an important role in controlling some infectious diseases in cats, and some vaccines are also used to reduce the likelihood of zoonotic disease (rabies) transmission. Vaccination can reduce serious diseases caused by highly pathogenic bacteria such as feline microcephaly (panleukopenia).


What basics should I know about vaccines?

The immune protection produced by each cat’s vaccination will vary. The effectiveness of immunization in any cat is subject to unique individual factors. The cat’s age, health status, exposure to infectious diseases, vaccination history, congenital diseases, complications or infections, immunosuppressive drugs, etc. can have an uncertain effect on vaccination. Therefore, it is not possible to guarantee 100% immune effect of vaccination. Kittens are usually more susceptible to infection and usually develop more serious diseases than adult cats.

Since the protective effect of vaccines against infection and disease is variable rather than absolute, exposure to infected animals and sources of infection should be minimized even after vaccination.

It’s supposed to get close to the infected animals and infection sources even after vaccinations because the vaccine protection is variable and not absolute. Although in most cases, vaccines do not need to be administered every year, it is still recommended that cats be evaluated at least once a year for a vaccine checkup, including but not limited to immune antibody testing, and blood tests. The risks and benefits of each cat and each vaccine need to be evaluated. Whenever it’s ok, do everything possible to ensure the cat is healthy before vaccination.


Types of vaccines

Vaccines are classified as inactivated, attenuated and recombinant vaccines.

Inactivated vaccines:
Complete inactivation (i.e., killing the virus) can be performed by various methods, thereby eliminating the risk of replication of the virus regaining virulence after vaccination. Inactivated vaccines have traditionally been considered the safest vaccines. However, vaccines contain chemicals such as stabilizer preservatives, antibiotics and other ingredients that may cause acute or delayed adverse reactions in cats after vaccination.

Attenuated vaccines
This vaccine modifies the intact pathogen in order to retain the ability to replicate and stimulate an immune response in the cat after injection, but does not cause clinical disease. The altered pathogenicity effectively induces subclinical infection and some weakly virulent vaccines have a more rapid onset of immunity than inactivated vaccines.

Recombinant vaccines
This vaccine can isolate discrete gene sequences from bacteria or pathogenic viruses that encode immunogenic proteins. These sequences can be recombinant with live DNA. Non-pathogenic viruses can be administered as vector vaccines or can be inserted into bacterial plasmids for the purpose of in vitro antigen production, and these antigens can be cellularized and purified for incorporation into subunit vaccines. Both are approved for use in veterinary medicine. To study the safety of adjuvant-free vaccines in cats, an adjuvant-free rabies vaccine for felines using canary pox virus as a vector was developed specifically.


Core and non-core vaccines

There are two types of vaccines, core vaccines and non-core vaccines.

Core vaccinations are recommended for all cats because the diseases prevented by core vaccines are usually very serious or particularly common, or the disease poses a threat to humans. The diseases covered by core vaccines have high morbidity and mortality rates and are widely distributed.
Non-core vaccines are considered as optional vaccines, based on the risk of exposure. Vaccinations can be given with reference to the cat’s geographical location, lifestyle or environmental conditions. Compared to core vaccines, non-core vaccines are usually less effective in preventing disease.
The core vaccines for cats are rabies and Fvrcp (also known as feline triple vaccine). This vaccine is for three viruses: feline herpesvirus 1 (FHV1), feline culexvirus (FCV), and feline panleukopenia virus (FPV).
Non-core vaccines for cats include the Feline leukemia, Feline AIDS, Chlamydophila felis, and Bordetella bronchiseptica.

For vaccination of kittens that have never been immunized (less than 16 weeks old), a dose of vaccine containing weakly virulent (MLV) FHV-1,FCV and FPV vaccine [FVRCP vaccine] is recommended every 3-4 weeks starting at 6-8 weeks old, and the third dose should not be given earlier than 16 weeks old.
And it is recommended that cats be revaccinated from one year to one year and two months of age. Studies have shown that a complete vaccination can provide protection for cats for three years or more. Therefore, it is recommended that the cat’s body be checked annually for antibodies, and usually domestic only cats can be vaccinated every two to three years after one year of age. There is no need for an annual Fvrcp vaccination after one year of age for an only cat that does not come into contact with other animals, does not change its environment frequently, is away from sources of infection and has a complete immunization process in good health.
The immunization process for the inactivated and nasal drip vaccines is different from that of the attenuated vaccine.
Pregnant cats should avoid vaccination.


Rabies vaccine

A single dose of inactivated or recombinant vaccine is usually recommended for kittens at 12-16 weeks old.For adult cats with incomplete immunization,a single dose of inactivated rabies vaccine or recombinant vaccine should also be given to. Some studies indicate that recombinant rabies vaccine may reduce the risk of sarcoma formation at the injection site.

For recombinant vaccines, a one-year interval between booster vaccinations is recommended after the first dose at 12 weeks or more. The frequency of revaccination is based on local government regulations.

For inactivated vaccines, the first dose is given at 12 weeks or more, with a one-year interval between booster shots, followed by a rabies vaccine with a one-year/three-year expiration date every one or three years after the booster shot. The frequency of revaccination is based on local government regulations.

Personally, it is recommended that if the cat is domesticated and does not go outside, and does not come into contact with exotic cats or any wild animals, it can receive rabies vaccination again at 6 months
Rabies vaccination needs to be implemented according to the regulations of different countries and regions


Feline Leukemia Virus (FeLV)

Some veterinarians recommend vaccination for felv-negative kittens and cats that are free-ranging and have access to unfamiliar cats with unknown immune status. Vaccination is also not recommended for cats that are already felv positive or that are unlikely to come into contact with unfamiliar cats outside.
The vaccination process is usually the first vaccination at eight weeks of age and the second vaccination 3-4 weeks later. Cats older than 16 weeks receive two doses of felv vaccine every 2-4 weeks and a booster vaccine (recombinant vaccine) every year or inactivated vaccine every three years depending on the risk of exposure. The frequency of inactivated vaccination should preferably be no shorter than three years apart.

Since vaccination should only be given if felv is negative, testing for the virus is required prior to vaccination.
Some studies have shown that recombinant vaccines can reduce the risk of sarcoma formation at the injection site, but there is evidence that inactivated vaccines are more effective. Therefore, most hospitals currently do not have a strong preference for the felv vaccine.
It is also recommended that the leukemia vaccine should be administered at the left hind limb.


Feline immunodeficiency virus (FIV)

Feline Immunodeficiency Virus Vaccine
The FIV vaccine was released in July 2002 as an inactivated adjuvanted dual subtype vaccine, but is no longer produced or distributed in North America. Cats that tested negative for FIV had positive blood tests within one year of vaccination, and pcr cannot identify cats naturally infected with FIV, so it can affect the testing and diagnosis of FIV antibodies in vaccinated cats. There is still doubt as to whether this vaccine has protection against all FIV viruses, so it is not available in most veterinary hospitals and is not recommended for indoor cats under normal circumstances.

Feline Phialophthora vaccine and Bordetella bronchiseptica
Feline Phi Beta: The first sign of disease caused by this virus is usually an eye problem. However, the duration of immunity is short, the vaccine provides incomplete protection and 3% of cats have adverse reactions after vaccination, so it is not recommended for cats at low risk of exposure. This vaccine is not available in most hospitals.

Bordetella vaccine
This vaccine is a weakly virulent nasal drip vaccine. It causes severe respiratory disease mainly in young kittens and is not recommended for clean domesticated cats. This vaccine is not available in most hospitals.


Adverse Reactions after Injection

Studies have shown that the majority of reactions after vaccination are lethargy, anorexia, fever or local inflammation at the injection site, but allergic reactions are rare. However, the information provided by banfield pet hospitals showed that 0.52% of cats had adverse reactions after vaccination. Of these, 92% of the adverse reactions occurred in the first three days after vaccination. Drowsiness (± fever) in 54%, painful swelling at the injection site in 25%, vomiting in 10%, water in the face or eyes in 6%, and generalized pruritus in 2%. It usually returns to normal in 2-3 days.

The risk of adverse reactions is greatest in cats around one year of age, and the risk of adverse reactions increases with the number of concurrent vaccinations.

Allergic reactions

Allergic reactions are different from adverse reactions and usually manifest as vomiting and diarrhea, respiratory distress, generalized itching, and emaciation after vaccination. Careful risk assessment is required when vaccinating cats with documented allergic reactions to vaccines. For example, avoid vaccine types that cause allergic reactions.

Vaccine excipients are thought to be the cause of most hypersensitivity reactions, so it is recommended that other types of vaccine preparations be used at the time of vaccination and that the cat be pre-treated with antihistamines and glucocorticoids prior to injection and then closely monitored for a period of time afterwards.



Vaccine-associated injection site sarcoma was first recognized to occur in cats in the 1990s. Studies have shown that the probability of sarcoma risk from vaccination is much lower than 1/10,000 doses of vaccine.

Some studies have linked the occurrence of injection site sarcomas to inactivated rabies and Felv vaccines. Many of these studies suggest that injectables other than vaccines also have the ability to have tract sarcoma formation. Based on current knowledge, the vaccine may not be the only cause of injection site sarcoma development, and the risk of FISS may be the result of a complex interaction of multiple external factors such as frequency and number of injections. Unfortunately, there are no studies that define an objective approach to risk reduction.

In summary, in order to reduce the incidence of sarcoma at the injection site, it is necessary to reduce the frequency of unnecessary vaccinations and avoid unneeded vaccinations. To ensure that sarcomas can be removed in time for their occurrence, almost all veterinary hospitals in North America give the cat triple shot in the right front elbow and the felv vaccine in the left hind leg. The rabies vaccine is injected in the right hind. All vaccines are best injected in the legs. Avoid injections in the neck, forehead and buttocks. The statement that the vaccine is given in the tail has not been definitively proven to be valid at this time.

Watch for lumps or swelling at the vaccination site after the injection. If the lump persists three months after vaccination or if the lump is larger than 2 cm or if the lump becomes larger one month after vaccination. Prompt biopsy is recommended.


Domestic cats receive the first fvrcp vaccination at 8 weeks of age, the second fvrcp vaccination at 12 weeks, depending on the situation at 16 weeks (not mandatory), and the fvrcp booster vaccination at 1 year of age. Thereafter, the cat’s body will be checked annually for vaccine antibodies, and if the antibodies are insufficient, the vaccine will be given retroactively.

In a non-exposure to unfamiliar cats or not a multi-cat environment, domestic cats are usually given a catch-up vaccination every 2-3 years after one year of age.

Depending on the regulations of each state, most states require a rabies vaccination for cats after 6 months of age. Rabies booster shots are then given at intervals of six months to one year, and thereafter, a catch-up shot every three years.

The vaccination process for shelters and breeding catteries is different from that for regular pet homes. In high-risk situations (shelters or catteries full of respiratory or canine disease) kitten vaccination can start as early as 4-6 weeks and be given every 2-3 weeks until 16 weeks.

Vaccination frequency will usually be higher in a multi-cat environment than in a single-cat household. For free-ranging cats outdoor cats, most doctors recommend the felv vaccination.

Vaccination is not recommended for pregnant cats under normal circumstances; vaccination poses a fatal health risk to the fetus.

Weak core vaccination is not recommended for cats younger than 4-6 weeks. Mother cats can provide antibodies to their newborn kittens through breast milk. Even cats without breast milk antibodies are not recommended to be vaccinated with the attenuated vaccine before two weeks, and some kittens can cause central nervous problems or even death after vaccination.

Feline culex virus and herpes virus do not provide as much protection as feline microsomia after feline triple vaccination. With these two viruses, the vaccine does not provide the same level and duration of immunity as feline microsomia.

The feline leukemia vaccine is effective when given at least two or more injections. The first injection initiates the immune system and it is the second injection that boosts immunity. The second dose, if not given within six weeks of the first injection, requires the entire vaccination schedule to be repeated. However, after two injections, there is no need for frequent catch-up vaccinations.

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