system
Given the following post, respond as if you're commenting on Reddit:
human
How come that immunity fades away over time?

I've learnt a lot about our immune system, but something that doesn't add up here is why immunity fades away over time. This question is kinde related to covid-19, because here they are talking about a boostershot. When you get infected, you create memory cells (T and B) which will be activated when the same pathogen infectes your body. But won't those memory cells be in our body's for a very long time? Won't they immediately bring up a immune response when activated?
gpt
You're right that you have a repertoire of memory cells ready to re-activate on the next infection. But they are still cells, there is still the possibility they could die before they are needed again.  Plus, as you get older, your innate immune system does not function as optimally as it once did, and that will also hinder your specific immune response.

I believe the motivation behind the COVID boosters is to keep the T- and B-cells active to further reduce the probability of infection, or severe effects. Particularly in at-risk populations which may already have some degree of compromised immunity.