Noteworthy, when controlling for potential confounders/predictors (i.e., age, sex, Charlson Comorbidity Index, obesity, smoke, anti-N IgG positivity at baseline and/or during follow-up), anti-S IgG waning was confirmed negatively associated with CD4/CD8 ratio [β = –0.3336 (95% CI: –0.5594, –0.1079), P = 0.0043] and CD4+CD127+ percentage [β = –0.0175 (95% CI: –0.0297, –0.0054), P = 0.0052], while positively with CD8+CD38+CD45RO+ percentage [β = 0.1262 (95% CI: 0.0165, 0.2360), P = 0.0247] (Fig. 1f). Here, CD4 is linked to obesity due to melanocortin 4 receptor deficiency.