Question

In humans activated T-lymphocytes persist until end of life, and activated B-lymphocytes persist many years, so most vaccines don't need to be reapplied and the few that do are reapplied after 10 to 15 years (recommendation varies slightly by country).

However cats (and dogs) are vaccinated every year, with individual vaccines reapplied after one, two or three years.

Does the immune system of cats differ so that it loses the activated lymphocytes faster? Or why are the vaccines (recommended to be) reapplied so often?

Answer 1

The immune systems of cats (and dogs) may lose activated lymphocytes faster than humans, which is why their vaccines need to be reapplied more often.

Step-by-step explanation:

The reason vaccines for cats (and dogs) are reapplied more frequently compared to humans is because the immune systems of cats (and dogs) may lose activated lymphocytes faster. When a pathogen is encountered, B and T memory cells are produced to provide immunity. However, if the pathogen is not encountered again, these memory cells gradually die off. As a result, cats require more frequent vaccinations to ensure continued protection against diseases.