Anti-nucleocapsid IgG antibodies in SARS-CoV-2 recovered health care workers: One year follow-up study.

Objective: The objective of this study was to evaluate the magnitude and durability of the anti-nucleocapsid-IgG antibody titer in healthcare workers previously infected with SARS-CoV-2 for a period of 12 months. Methods: This study examined blood samples for SARS-CoV-2-specific IgG collected periodically from 120 healthcare workers previously infected with SARS-CoV-2 (confirmed by RT-PCR) and followed longitudinally up to 12 months from their enrolment into the study. Results: The median anti-N-IgG antibody level identified at 3 months was 23.7 CO-index (IQR: 9.13-50.27) and increased to 32.9 CO-index (IQR: 11.8-84.4) at 6 months. At 9 months, the median anti-N-IgG antibody level started to wane in the subsequent time and was dropped to 14 CO-index (IQR: 3.4-37.6) and declined further to 9.8 CO-index at 12 months (IQR: 2.8-9.8). When classified by age groups, the only statistically significant difference in anti-N-IgG between the two age groups (≤30 years and >30 years) was identified at 12 month time point (median difference 8.06, p = 0.035). Spearman correlation coefficient was negatively associated between anti-N-IgG and time interval ( r = -0.255, p = 0.000) but was not statistically significant with age of a patient ( p > 0.05). Conclusions: In conclusion, SARS-CoV-2 antibody levels started declining after 6 months but remained detectable in the majority of patients up to 12 months.