Cloud
Mlem
AIUI immunity could be for life. In SARS1 it's been like 20 years or however long since. What happens is the same as any other virus - after the antibodies fade (3-6 months by the looks of it), you get an infection and the memory cells are like "ah right it's this shit again" and triggers the creation of new antibodies, which takes a couple of days, so you feel a bit cruddy in the meantime. But not long enough for serious symptoms to kick in. Then they make short work of it...
I think the boosters are to a) tweak for variants so that immunity doesn't fall behind while the virus eventually theoretically mutates beyond recognition (in the worst case) and b) to keep those antibodies from fading while we're fighting waves of the thing, making it easier to control spread.
as always I could be talking bollocks, it's just what I understand of it from following it for 18 months
I think the boosters are to a) tweak for variants so that immunity doesn't fall behind while the virus eventually theoretically mutates beyond recognition (in the worst case) and b) to keep those antibodies from fading while we're fighting waves of the thing, making it easier to control spread.
as always I could be talking bollocks, it's just what I understand of it from following it for 18 months