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How Vaccines Work (And Why Over-Vaccinating Can be Harmful)

For years, veterinarians promoted a vaccination program as the focal point of preventative medicine. Every animal received every vaccine available each year, regardless of the animal’s medical history.

We now recognize that it is not always necessary to give our feline friends every vaccination; in fact, over-vaccinating can even cause more harm than good.

Here’s why: vaccinations protect by stimulating the immune system to produce substances called antibodies, which are created in response to a foreign protein in the bloodstream.

When the body is later exposed to a natural (non-vaccination) form of the organism after being vaccinated against it, a “memory” process takes over and begins to produce new antibodies that bind to the organism and remove or inactivate it.

Although in most cases vaccinations are excellent protection against illness, there is some evidence to suggest that, on occasion, vaccinations can overstimulate the immune system and actually cause harm.

Why Our Approach to Vaccination is Safest for Your Cat

At the Scaredy Cat Hospital, we tailor a vaccination program to each individual cat.

Only the necessary and most important vaccines are administered. We make these decisions based on your cat’s unique needs and medical history. This way, your cat gets optimal protection against illness, with the lowest possible risk.

Vaccinations: A Suggested Course

We use the following recommendations as the starting point for tailoring a vaccination course for each of our feline patients.


  • FVRCP: Feline viral rhinotracheitis, calicivirus, and panleukopenia. Given at 8, 12, and 16 weeks, at 1 year, then a booster vaccine every 3 years.
  • RABIES: To reduce risk of sarcoma, we use Purevax rabies vaccine, which may be administered as early as 8 weeks old, and requires annual boosters.


  • FELV: Feline leukemia virus vaccination should be given if there is potential exposure to another cat of unknown vaccine status (i.e.: outdoor cats). The initial vaccine needs to be “boosted” in four weeks and then annually. All cats should have a negative FeLV test before vaccinating.
  • FIV: Feline immunodeficiency virus (feline “AIDS”) vaccine: as with FeLV vaccine.
  • GIARDIA: Only in refractory cases of Giardia. It consists of two vaccinations separated by four weeks.
  • RINGWORM: Only in refractory cases of ringworm.
  • FIP: Feline infectious peritonitis vaccine is not recommended.

Be Aware: Possible Allergic Reactions to Vaccines

Vaccinations are not always without complications. It only happens rarely, but sometimes a true allergic reaction can occur in response to a vaccination.

Vomiting is always the first sign, and happens shortly after the vaccination is given.

Because this can quickly progress to a life-threatening condition, you should notify your veterinarian immediately if it you notice symptoms of allergic reaction.