Vaccines help prevent infections, everyone knows this. They work by exposing the animal (or a person) to a virus or bacteria (or a specific protein from a virus or bacteria) that has been modified to make it incapable of causing disease. The body mounts an immune response to that specific disease causing agent and produces antibodies - special proteins that act like seeking missiles. When the animal is exposed to the virus or bacteria in the future, these antibodies target the body's cells to destroy the invading cells before signs of the disease occur.
So why do vaccines need to be given yearly? Antibodies are already present, right? The short answer is yes, but the body is a very complex system. Over time, antibody production is decreased if the body is never exposed to the virus or bacteria in the vaccine. If a dog isn't vaccinated for 5 years, he may no longer have enough of an immune response to prevent disease. There is research being done that shows most animals probably don't need yearly vaccines; we can measure response to a vaccine over time by measuring titers - or how much antibody is present in blood or other sample. The problem we run into is finding the right time to revaccinate an individual animal. Just like with people, each animal's response to a vaccine is different and can can be affected by health at time of vaccine, age, stress, and many other factors. Without doing a titer, we simply don't know how effective our vaccine was and how much protection the animal is still getting from a previous vaccine. Titers are expensive (usually $50-100 per virus or bacteria) so generally we elect to booster a vaccine rather than testing.
Vaccines are generally very safe, but they can cause side effects. Cats in particular can develop a type of cancer called a sarcoma often in association with vaccines. This is rare (1 in 1,000 to 10,000 cats) and the tumor can also occur in cats that have never been vaccinated, but the tumor can be quite aggressive. To minimize risk of this negative side effect, most veterinarians have changed vaccine protocols for cats. At Cedar County Vet we follow the American Animal Hospital Association (AAHA) national guidelines for vaccines. Vaccines are given based on risk of infection: indoor only cats with limited exposure can be revaccinated every 3 years, while outdoor cats or those that live in households with a known infection (such as a leukemia positive cat) receive yearly vaccinations. This takes into account the pros and cons of vaccines and attempts to reduce risk for vaccine reaction as much as possible while maintaining the protection of vaccines.
Stay tuned for our next blog post which will cover kitten and puppy series and explain why coming in every three weeks is so important (and worth wrecking havoc with your schedule!). As always, if you have any questions about your animal's care or any of our policies please ask as your pet's health and well-being is our primary concern!
- Dr. Kris Hubbard