It has always been my understanding the cold is always a different one that your system does not recognize. Immunity is not just antibodies but DNA memory that mounts an early defense. Has that changed?
Nope. Not changed but your understanding of immunity is incomplete. You have immune system memory cells that have variable longetivity. Sometimes they last and can mount a ferocious response to a new appearance of an old bacterial invader.
Viruses are different. Your body doesn’t always get rid of them, they sometimes just suppress them indefinitely until the immune system gets weak from age or stress. The chickenpox virus is like that. It can reappear as shingles.
Other viruses that are DNA viruses recode cell DNA and can even cause cancer.
Coronavirus is an RNA virus. It can linger in the body like other viruses. If it takes hold only in the upper respiratory tract, like some people who never get a cough or seriously ill. Then the immune system won’t mount as strong a response and it won’t necessarily preserve antibodies and memory cells very long.
If it infects the lungs, the immune response is much stronger there, so the immune system retains its defenses longer. Or we hope so.
Flu viruses are notorious for waning immunity, add that to frequent mutations, thus a yearly vaccine for it.
I don’t know if a vaccine will prove effective enough against it. I think it might be like some flu shots where there’s some match but it might not provoke enough of an immune response to really protect you.
This whole thing has given me a headache. I’m still hoping it mutates into a less virulent form and just becomes another annoying cold.