Core vaccines are considered vital to all cats and should be given to all kittens for they help protect the kittens against viruses and rabies. The following are the core vaccinations for kittens. First, panleukopenia (feline distemper), which can cause fever, diarrhea, dehydration and other neurological symptoms. Next, is feline calici virus and feline herpes virus type I (rhinotracheitis) that are responsible for upper respiratory infections in cats. Lastly, rabies, which is an inflammatory infection that specifically, affects the gray matter of the brain and central nervous system.