It remains to be seen over the long-run whether antibody levels correlate inversely with either risk of: a) _any_ Covid infection or b) _severe_ Covid infection

It remains to be seen over the long-run whether antibody levels correlate inversely with either risk of: a) _any_ Covid infection or b) _severe_ Covid infection. Antibody levels are often cited as prediction surrogates early on because they are easy to measure. Occurrence or recurrence of infection, irrespective of antibody levels, of course, takes time. Also remaining to be seen is the role of T-cell mediated immunity in reducing the severity of Covid infection. If that role is significant, then declining antibody levels may be less worrisome than people believe currently.