A few comments. Lots and lots of viruses infect, get defeated, and then can reinfect because immunity disappears.
Antibodies do not particularly “linger”. Specific cells create them. Antibodies do their stuff for a while and disappear quickly, because they are not immortal. It is the cells that create them that have to retain memory and replace the antibodies, and . . . there’s no law of the universe that says they will retain that memory for long periods. The titration density of antibodies fades. Memory cells don’t bother creating more. This titration measurement is how one knows how long a vaccine lasts. This is why 10 yrs between tetanus shots.
Stop thinking the virus will burn out. That’s another thing there is no law of the universe commanding it. Smallpox virus was with mankind for millenia and never burned out. Only human intervention erased it.
Thanks for that post Owen.