Good question. This is something I get asked all the time.
In Australia, there are a number of diseases that cats can be protected against through vaccination. These include: Feline Parvovirus (also known as feline infectious enteritis and feline pancleucopenia); Feline Herpes virus and Carlicivirus (the later two cause ‘cat flue’). Kittens usually receive 3 boosters between the age of 8 and 16 weeks and then yearly boosters are administered for life. Cats who venture outdoors should also be vaccinated against Feline Immunodeficiency Virus (FIV) and Feline Leukemia virus (FeLV) depending on your location. These viruses are spread through saliva during cat fights.