One question I have is do viruses like covid ever reach peak fitness? I assume there are properties of the virus that at some point cannot be changed because th

One question I have is do viruses like covid ever reach peak fitness? I assume there are properties of the virus that at some point cannot be changed because they will negatively affect the ability of the virus to reproduce and with universal vaccination maybe it can be cornered in a local maximum where it can’t optimize reproduction further without losing some ability to reproduce first. This is how I keep the thought of eradication alive :)