Starting from around 6-8 weeks, kittens will need a course of vaccinations to protect them against a range of prevalent feline diseases. This course will take 3-4 months to complete. Even if they are to be an indoor cat for their entire life, they should still get the five core vaccines: panleukopenia (feline distemper), feline herpesvirus, calicivirus, rabies and feline leukemia virus (FeLV). If you happen to adopt a cat without knowing its vaccination history, then you should assume they’ve had none and take them for the full course of at least those first four.The FeLV vaccine is recommended for kittens and outdoor going adult cats, but is not considered necessary for indoor adults.Once the initial round of vaccines are done, your cat will need an annual booster. “If you would rather not vaccinate annually, your vet may offer a blood titre test which measures the level of immunity still present to determine whether a booster is necessary,” says Dr. Boulay.