Cat & Kitten Vaccines

Perhaps no medical discovery has ever done more to protect the health and welfare of cats and other animals than the development of vaccines. Vaccines have been instrumental in reducing the incidence of preventable, infectious diseases in cats, helping to ensure that they can live longer, healthier lives.

Benefits of Vaccinations for Cats and Kittens

Some of the obvious benefits of vaccinating kittens are that they can avoid getting sick from contagious diseases. Unvaccinated cats are at risk of contracting potentially deadly diseases, such as calicivirus, distemper, and panleukopenia. Vaccines can also reduce the risk of secondary infections, which can be more serious and even fatal.

Zoonotic diseases, such as rabies, are diseases that can be transmitted from animals to humans. Vaccinating cats against these diseases helps protect not only the cats but also people who come in contact with them. Rabies vaccine is required by law in many states.

Benefits of vaccines reach far beyond an individual animal, however; when most cats in a given population are vaccinated, the risk of disease for all cats in that population is reduced. This so-called “herd immunity” can play a critical role in protecting cats in shelters and other community-based populations.

Explanation of the Procedure

Your veterinarian will examine your kitten to ensure they are healthy enough to receive the vaccination. This may include checking body temperature, listening to the heart and lungs, and examining the eyes and mouth.

If the physical exam is clear and the kitten is deemed healthy enough to receive the vaccine, your veterinarian will discuss the vaccine protocol with you, answer any questions you may have and administer the vaccination.

The process of vaccination is simple and quick and usually involves the injection of a small amount of a killed or weakened virus under the cat’s skin. The goal is to stimulate the cat’s immune system to produce antibodies that will protect the cat against future exposure to the virus.

For many commonly used vaccines, one injection is all that is necessary to provide protection against multiple diseases; as it combines multiple different antigens. This is known as a combination vaccine.

In many cases, vaccines will require boosters, or additional doses, to ensure the cat is adequately protected. Your veterinarian will be able to provide you with a schedule of boosters and other recommendations for your cat’s specific vaccine protocol.

When to Vaccinate?

Right after kittens are born, they have some protection from the antibodies they received with their mother’s milk, but this protection decreases as the kitten grows.

Kittens should receive their first vaccine at 6 to 8 weeks of age. This is the optimal time for their body to respond to the vaccine and start producing the necessary antibodies. Subsequently, kitten vaccinations should be administered every 3-4 weeks until they reach 16 weeks of age. The reason for that is the interference of maternal antibodies that kittens get when nursing from their mother, which can limit the effectiveness of the vaccines. These maternal antibodies wear off when the kitten is between 6 weeks of age and 14 weeks of age, most commonly between 9 and 12 weeks. We cannot predict the exact time this will happen in a given kitten, so it is best to vaccinate them according to the recommended schedule during this period.

If an adult cat is being vaccinated for the first time, or has not been vaccinated in a while, a booster vaccination 2 to 3 weeks later may be recommended. This is because the first dose introduces the antigen to the cat’s immune system, and the booster helps to ensure the cat is adequately protected.

For both kittens and adult cats vaccinated for the first time or after a lapse in their vaccine schedule, a booster is needed one year after the initial series of vaccines. After that, most cats need to be vaccinated every year or every three years, depending on the type of vaccine. Your veterinarian will be able to provide you with more information on the specific vaccine protocol for your cat.

For cats with minimal risk of exposure (e.g. strictly indoor cats) it may be safe to delay additional booster shots, provided they had a successful initial vaccination series, including the one year booster. This is due to the fact that the duration of the immunity provided by some vaccines can be longer than the normally recommended intervals.

You may have heard about tests that can be done to determine the immunologic status of your cat and the need for repeated vaccinations. Such tests, while promising, are not accurate or recommended for cats at this time. 

Side Effects and Risks Associated with Vaccines

Vaccines are generally very safe and effective (less than 1% of cats experience any adverse effects), however, as with any medical procedure, there are some side effects and risks. Please note, the fact that your cat did not have a reaction to one vaccine does not predict whether it will or will not have a reaction to another vaccine in the future.

  • The most common side effects of vaccination are mild and include discomfort at the injection site, lethargy, reduced appetite, and mild fever. These side effects usually resolve within 2-3 days. If they last more than that, contact your veterinarian right away.
  • Some modified live vaccines can cause mild, self-limiting clinical signs of the disease they are designed to prevent, such as mild coughing, sneezing, or nasal discharge after vaccination for respiratory viruses.
  • In very rare cases, cats may experience serious allergic reactions soon after vaccination, including anaphylactic shock, which can be life-threatening. Signs of a serious allergic reaction may include vomiting, diarrhea, facial swelling, difficulty breathing, and collapse. Contact your veterinarian immediately if your pet experiences any of these signs.
  • Although vaccines are generally very effective there is a small risk that a vaccinated cat can still become ill with the disease it has been vaccinated against.
  • Less common injection site reactions include the development of an infection, hair loss, hair discoloration, usually in the form of white or gray patches in the fur.
  • A very rare but a very serious concern is the development of an injection site sarcoma, or cancer at the injection site. This exceedingly rare complication has been associated with certain vaccines, mainly those containing aluminum adjuvants, and is deadly if left untreated. However, the incidence of feline injection site sarcoma is very low, for every 10,000 vaccinated cats, less than 1 will develop sarcoma. Because the treatment for this condition is surgical removal of the tumor, vaccines are given at sites on the body that allow complete tumor removal, if it should occur.

Core vs. Non-core Vaccines

Kitten vaccines are often classified as “core” or “non-core” vaccines. Core vaccines are those that should be given to all cats, regardless of their lifestyle or risk of disease exposure, except in cases where a cat has a medical contraindication or a specific health or lifestyle factor that may make vaccination inadvisable.

Non-core vaccines are those that may be recommended depending on a cat’s age, risk of disease exposure, or lifestyle (e.g. indoor or outdoor cat).

Not all cats need all available vaccines. It is important to discuss with your veterinarian which of the commonly used vaccines listed below are recommended for your cat to determine the best vaccine protocol.

Core vaccines for kittens and adult cats:

• Rabies (required by law in Florida and most other states)

• Feline panleukopenia (FPV)

• Feline herpesvirus-1 (FHV-1)

• Feline calicivirus (FCV)

• Feline leukemia virus (FeLV; core for kittens only)

Non-core (optional) vaccines for kittens and adult cats:

• Feline leukemia virus (FeLV; non-core for previously vaccinated adult cats)

• Feline immunodeficiency virus (FIV)

• Chlamydia felis

• Bordetella bronchiseptica

• Feline infectious peritonitis (FIP)

• Dermatophytes


Vaccines are not perfect, but the health benefits of vaccination for cats far outweigh the risks. Most cats with very few exceptions should receive at least the core vaccines recommended by veterinarians, to help ensure a long and healthy life. It is important to discuss with your veterinarian which vaccines are recommended for your cat and to follow the recommended vaccine protocol.