Longevity of Immunoglobulin-G Antibody Response Against Nucleocapsid Protein Against SARS-CoV-2 Among Healthcare Workers

Abstract

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the latest pandemic and the most significant challenge in public health worldwide. Studying the longevity of naturally developed antibodies is highly important clinically and epidemiologically. This paper assesses the longevity of antibodies developed against nucleocapsid protein amongst our health-care workers. Methods: This longitudinal cohort study was conducted at a tertiary hospital, Saudi Arabia. Anti-SARSsCoV-2 antibodies were tested among health-care workers at three-point intervals (baseline, eight weeks, and 16 weeks). Results: Of the 648 participants, 112 (17.2%) tested positive for Coronavirus (COVID-19) by PCR before the study. Of all participants, 87 (13.4%) tested positive for anti-SARS-CoV-2 antibodies, including 17 (2.6%) participants who never tested positive for COVID-19 using rt-PCR. Out of the 87 positive IgG participants at baseline, only 12 (13.7%) had remained positive for anti-SARS-CoV-2 antibodies by the end of the study. The IgG titer showed a significant reduction in values over time, where the median time for the confirmed positive rt-PCR subgroup from infection to the last positive antibody test was 70 (95% CI: 33.4-106.5) days. Conclusion: Health-care workers are at high risk of exposure to the SARS-CoV-2 virus, and contracting an asymptomatic infection is not unlikely. Developing and sustaining natural immunity differs from one person to another, while the rate of positive IgG anti-SARS-CoV-2 wanes over time.