Cat influenza can be a severely debilitating disease, and may be fatal in some cases. The vaccines currently available are very effective against these diseases -- but remember that your cat needs annual booster injections to keep her protected throughout her life.
Protecting your kitten from disease is an essential part of her early health care. Until she has have been vaccinated, she should remain indoors. Vaccinations require an initial round of injections, along with booster shots throughout her life.