system
Given the following post, respond as if you're commenting on Reddit:
human
After having Covid, your body retains antibodies against it for only a short period of time. Why does the body essentially "forget" these antibodies?

For other viruses and diseases, the body seems to remember its antibodies and resistances for much longer periods of time, if not indefinitely. What makes Covid so different that the body loses its antibodies for it after a relatively short period (roughly 90 days, iirc). Is it due to a function of the virus and its mutative nature, or is it a function of the body itself?

And as a side question, what does the vaccine do that allows the body to keep these tolerances and antibodies longer?

EDIT: Thanks for all the helpful responses! I don't know very much at all about how viruses work and the amount of information here about antibody lifespans, how the immune system creates them, and the miscommunications by the media regarding how immunity functions has been quite eye opening. I wish I would have worded the title better, but at least there's now plenty of responses to illuminate the error there as well!
gpt
You lose antibodies to many diseases over time. This is because there's no reason for your body to be expending time and energy to mass produce antibodies when the threat is gone. The key idea (that these studies do not test for) is the presence of T-cells that are dormant but are reactive against these pathogens. Re-challenge would lead these cells to proliferate and activate a whole cascade that results in more plasma cells producing antibodies.