group of kittens

Cat breeders have a critical role to play in assuring that the kittens they raise and sell are properly vaccinated and remain healthy.

There are core vaccines that all cat breeders and owners should give to their kittens, starting as early as 6 weeks of age, but preferably waiting until 8 – 10 weeks of age.

The Vaccines

The vaccines include:
• (panleukopenia) parvovirus virus (FPV) vaccine
• feline calicivirus (FCV) 47 vaccine
• feline herpes virus-1 (FHV-1) vaccine
• in some countries, the rabies virus (RV) vaccine

Revaccination 

Revaccination of kittens should occur so that the last dose of vaccines is given between 14 –16 weeks of age. Therefore a two dose or three dose schedule can be used to ensure that all cats are protected from the diseases caused by these viruses.

A two dose schedule, with modified live vaccines (MLV) would, for example, be at 8 and 14 weeks, or 10 and 14 – 16 weeks, whereas a three dose schedule could be 8, 12 and 16 or 10, 13 and 16 weeks.

The intervals between doses of MLV (infectious) vaccines are not as restrictive as those between killed (non-infectious) vaccines.

Two doses of killed vaccines are almost always required and the interval between those doses should not exceed 6 weeks, whereas when the first dose of an MLV vaccine is given, it should be at least 2 weeks before the second dose is given, but this period can exceed the 6 week maximum interval required for killed (non-infectious) vaccines.

Although MLV vaccines are generally effective when only one dose is given in the absence of maternally derived antibody (MDA), some cats given the combination core vaccine require two doses to mount an antibody response to the FCV and/or FHV-1 vaccines. Therefore, a minimum of two doses is recommended, even when cats are first vaccinated at 16 weeks of age or older, at a time when the kittens no longer have MDA.


The FPV vaccines, especially the infectious (MLV) vaccines, are highly effective, having a 99% efficacy when the last dose is administered at 14 – 16 weeks of age. In contrast, the efficacy is much less for the FCV and FHV-1 vaccines (estimated at 60 – 80%), due to the nature of the viruses and the diseases they cause.

Respiratory and other mucosal surface diseases, such as the feline respiratory disease complex (FRDC), are much more difficult to prevent than systemic 48
diseases like feline panleukopenia. The other core feline vaccine recommended for cats in certain, but not all, countries is rabies vaccine. When available, a modified live rabies virus can be used, but most rabies virus vaccines are killed adjuvanted vaccines or, in certain countries, a viral vectored recombinant rabies vaccine is available. When rabies vaccines are given, you must follow the regulations for your country as to when they should be given and how often they are required.

Revaccination of cats with the core vaccines FPV, FCV, FHV-1 is recommended at 1 year of age or 1 year after the last kitten vaccines, then not more often than every 3 years. Some veterinarians prefer to give the FCV and FHV-1 vaccines yearly because those vaccines are not as effective as the FPV. However, studies have not been done to show that yearly revaccination provides better protection than the triennial vaccination.


Two additional and very important infectious diseases of cats that could be significantly reduced, if not eliminated, through identification and elimination or isolation of carrier cats and vaccination of susceptible cats are feline leukaemia, caused by feline leukaemia virus (FeLV), and feline immunodeficiency disease, caused by feline immunodeficiency virus (FIV). Both of these diseases are caused by retroviruses that are found only in the feline species.

Excellent diagnostic tests are available to detect ‘carrier cats’ that serve as the primary source of infection for susceptible cats. If the carrier cats were eliminated, these diseases would disappear from the species. Therefore, it is essential that all cats used for breeding purposes be tested for FeLV using a reliable FeLV antigen detection test and for FIV using a reliable FIV antibody test or a polymerase chain reaction (PCR) test. Neither FeLV persistently infected (test positive) nor FIV infected (test positive) cats should be used for breeding. Furthermore, kittens born 49 to FeLV and FIV negative queens should not be housed where FeLV or FIV positive cats live or visit. The reason is that young kittens are highly susceptible to infection with both of these viruses. When young kittens are infected with FeLV, they have a high probability of becoming persistently viraemic (carrier cats) for life, thus serving as a reservoir for new viral infections. Furthermore, FeLV and/or FIV infected males should not be used for breeding purposes, as they can infect the queens and when the infected males are present in the household, they serve as an important source of infection for the newborn kittens.


Although FeLV vaccines are available in most countries and FIV vaccine is available in a few countries, elimination or isolation of the positive carrier cats will do more to prevent these diseases in the population than the vaccines alone. These vaccines are not considered core (e.g. vaccines every kitten should receive), however, vaccination, especially with FeLV is highly recommended for kittens.

Vaccination should begin as early as 8 – 9 weeks, followed by a second dose (required for all FeLV vaccines) 2 – 6 weeks later. When the second dose is not given within 6 weeks of the first, two doses should be given, again making certain that the second dose is 2 – 6 weeks after the first. The FeLV vaccine should be given again at a year of age and then not more often than every three years. The FIV vaccine, even if available, is not recommended, because vaccination will interfere with the serological diagnostic test (e.g. make it positive), as this relies on antibody, and the PCR diagnostic tests available at this point in time are not always reliable. Furthermore, the FIV vaccine currently available is not proven to provide protection against all clades (strains) of FIV, thus even vaccinated cats can become infected and shed the virus.


With the virus testing and the core vaccination schedule suggested above, it would be expected that your cats should remain free of the vaccine preventable diseases for a lifetime. However, it is important to understand that FRDC is very complex and many things contribute to this disease. Thus, FRDC is not vaccine preventable and the best you can expect from the vaccines that are available (FCV, FHV-1 and others like Chlamydophila and Bordetella) is reduced severity of disease signs. However, a vaccination program with the core vaccines and control and elimination of FeLV and FIV carrier cats will lead to a much healthier cat as well as a much healthier population of cats.


Adverse events from use of feline core vaccines are in general uncommon. The two most severe adverse events seen in the cat are anaphylaxis that, if not treated immediately with epinephrine (adrenaline), can be lethal, and feline injection site sarcomas (FISS) that are generally lethal whether treated or not. Both of these severe adverse reactions can occur at a prevalence of between 1 in 1,000 to 1 in 10,000 vaccinated cats. A cat with a history of anaphylaxis should not be revaccinated with the offending vaccines (if these are known). Affected cats with a history of this adverse reaction should be tested for antibody to FPV. When antibody is present to FPV, regardless of titre, the cat should probably not be revaccinated with any vaccines. Due to the high mortality associated with FPV disease, it is critical the cat is immune (antibody positive) for the FPV virus.
There are many types of feline vaccines available to prevent the core diseases. They include infectious (MLV/attenuated) vaccines and non-infectious (killed, inactivated) vaccines. Some of the infectious vaccines can be given intranasally and others are for systemic (intramuscular or subcutaneous) injection only. It is 51
critically important that the vaccine be given according to the manufacturer’s recommendation on the label. If a MLV core vaccine that must be given systemically is given locally (e.g. intranasally or conjunctivally), the vaccine may cause disease. In contrast, a killed vaccine that must be given systemically and always requires two doses, if given locally will provide no protection. Both infectious (MLV) and non- infectious (killed) vaccines can be effective in preventing disease and both types are often used in vaccination programs. In general, infectious core vaccines are the most effective and they are often the safest as they are less likely to cause adverse reactions, especially hypersensitivity reactions and FISS compared with non-infectious (killed) vaccines.


Your veterinarian will provide the safest and most effective disease prevention programme for your cats, which will include vaccination with both infectious and non- infectious vaccines and diagnostic testing for diseases like FeLV and FIV to help eliminate these diseases.