Long-Term Persistence of Anti-SARS-COV-2 IgG Antibodies.

Antibodies against severe acute respiratory syndrome coronavirus-2 (Anti-SARS-COV-2) can be detected in patients with COVID-19 in 7 to 10 days post onset of symptoms (POS). However, there is no firm evidence of the long-term persistence of these antibodies in recovered COVID-19 patients. Therefore, this study aimed to evaluate the stability of anti-SARS-COV-2 IgG in recovered COVID-19 patients in a 15-month follow-up testing. Thirty hospitalized patients with real-time PCR-confirmed SARS-COV-2 infections were included in the study and five serum samples (1st, 2nd, 3rd, 4th, and 5th) were collected from each participant. The serum levels of N and S specific anti-SARS-COV-2 IgG and IgM antibodies were evaluated by the immunoassay technique at the same time. To determine the correlation between levels of anti-SARS-CoV-2 IgG/IgM with severity of disease, neutrophil-to-lymphocyte ratio (NLR %), and the serum levels of C-reactive protein were evaluated using an automated analyzer and turbidimetry assays, respectively. The mean serum level of anti-SARS-CoV-2 IgG antibody was at the highest level up to 90 days and then decreased significantly 1 year POS (P < 0.0001). However, it was still detectable in a 15-month follow-up testing. There were no significant differences in the mean levels of IgG antibody in patients with mild, moderate, and severe diseases. The results from this study suggest that the titer of anti-SARS-COV-2 IgG antibody is detectable at high levels up to 3 months and then decreases over time. However, these antibodies can be reliably detected in up to 15 months, and they may persist for a long time.