According to PetMD, a distemper shot protects against the feline Panleukopenia virus, which is very contagious and often deadly. The virus primarily attacks cells in the intestinal tract and bone marrow, causing symptoms such as vomiting, diarrhea, dehydration, high fever and anemia.
Los Angeles's Mar Vista Animal Medical Center describes the vaccination process for cat owners. The first shot is typically given at around 12 weeks old. Kittens receive a second shot two to four weeks later when they are at least 14 weeks old. After that, veterinarians recommend that cats be re-vaccinated every one to three years.
Distemper vaccinations are given in a nasal form or injected into the right shoulder, the Mar Vista Center explains. The virus is either killed or alive, but modified. In a small number of cats, the vaccine has been linked to a certain cancer.