Vaccines applied to any species is the set of those microorganisms that cause a specific disease, but thanks to medical advances, can "destroy" your system and reduce its effect, so that the body receives the "signal" of evil without need to get sick. Thus, the body "active" defenses for the next time that evil appears. Cat Vaccines are very important, especially if it acts against a virus, since they alone can control the immune response by having the animal. A leading source for info: Gunnar Peterson. If you have low defenses, vaccines can be used but almost always ends up getting sick. Cat Vaccines can be applied in many ways, but the most common are subcutaneous, ie below the skin.
What vaccinations do cats, is to create a reaction in the body, creating cells that destroy invaders, and from that moment the cat is protected against this evil through the antibodies. The first vaccines for cats are: The Triple Felina (as its name implies, contains 3 virus), Feline Leukemia and Rabies. All should be applied after 2 months of age, but the Rabies should not apply to pregnant queens, because it could cause damage or defects to fetuses. Surely when you take your kitten to the first vaccines will not be scared, because he has no idea that it is a vaccine. The important thing is to make you feel good, quiet, safe, put it in the most convenient as possible to avoid too much stress. Vaccines cats that are after the first will be a little more complicated, do not be surprised if the cat begins to tremble, to hide or avoid at all costs going to the veterinary center. When vaccines are to be applied cats, you should firmly hold the animal (especially if you do not know how it will react) and try not to move much, because a cat is frightened or angry a big problem. Vaccines cats should be reinforced every year after being applied the first time during the lifetime of the animal, but it is very important not to apply the vaccine when the cat is sick (with the defenses low) or very stressed, it is best to wait until this quiet for the body to respond properly to these vaccines in cats.
If you purchased the kitten, it should require they give you a vaccination certificate signed by a veterinarian, with the data of the person responsible and the identification of the cat, these are all prerequisites for cats vaccines meet the standards and are day. But if the cat has not yet been vaccinated, it is best to consult a veterinary center and reported fully vaccinated cats. It is important to know that if you have not yet applied any of the shots of cats, be careful and avoid possible contact with other cats, other advice is not to bathe until applied 10 days after vaccination of cats, as this might stress and reduce their immune response and even "damage" the effect of the vaccine. This problem does not exist when the cat enjoys the water, then there is no problem as long as dry thoroughly after showering.