A trend analysis of Sars-Cov-2 anti-nucleocapsid IgG antibodies with a recommendation of the cut-off classification to identify naïve, vaccinated, and infected cases

Determination of the vaccination’s effect on immune responses with emergence Sars-Cov-2 pandemic become an important issue. This study aimed to evaluate response anti-nucleocapsid IgG (anti-N IgG) index in naïve, vaccinated, or infected cases, addition suggesting ‘How distinguish between vaccinated versus cases via anti-N IgG?’. Anti-N levels naïve [0.03 (0.02–0.06)], [0.7 (0.2–1.96)], and [3.07 (1.44–5.2)] groups were statistically different (p<0.0001). all periods sub-groups An inter-group analysis repeated tests established that there was no difference not-vaccinated (-1.44±1.27) after-infection early-vaccinated (-1.62±0.93) (p=0.717). A significant observed late-vaccinated (1.5±1.61) Three-category cut-off calculated for naive, as ≤0.32, 0.32–1.40, ≥1.40 respectively. The area under receiver operating curve (AUROC) this classification 0.907 (95% CI, 0.879–0.930) AUROC manufacturer's (≥1.40) 0.790 0.754–0.823) demonstrates early vaccination after infection does not affect trend level. manufacturers should set out update their dating back pre-vaccine period post-vaccine period.