Immunization can help protect the cat against some infectious diseases. Vaccinations trigger the production of antibodies against certain microorganisms, making a cat immune to many diseases without causing the symptoms of the disease.
For example, cats can be vaccinated against feline infectious enteritis, feline herpes virus, and feline calcivirus.
Stress
Cats are easily stressed. A change at home is often the cause, such as the arrival of a new pet or baby, or even the rearrangement of furniture. Stress causes the release of hormones such as epinephrine (adrenalin) and cortisol.
In the short term, these hormones increase awareness and energy but if their release is prolonged, they dampen the immune system, impairing a cat’s ability to protect itself against infections and cancer and to recover speedily after illness.
Chemicals called endorphins are released by the brain when a cat is highly excited, such as during a fight with another cat or animal. In such cases, endorphins have a protective role because they are natural painkillers, lessening the discomfort of any teeth and claw wounds inflicted.