YS > lot of people I know who don’t want to get immunized because they have antibodies were tested positive for antibodies months ago and never actually showed COVID symptoms nor tested positive at any point.
non-professional understanding of theory: I think the issue is with T-cell protection. Antibodies are very specific and may be less effective with new variants. T-cell immunity is not helping with initial infection, but kicks in later to protect against serious disease and are also longer-lasting. T-cells generalize better and should be more protective against variants. Light cases of disease might not generate T-cell protection at all. Vaccines do, and possibly AZ and J&J more than mRNAs.
Bottom line, suggest to them to get one vaccine, with their initial disease working as a prime.