Long-term follow-up of SARS-CoV-2 IgM and IgG production in the patients with COVID-19 in Japan

Introduction: It is known that Coronavirus disease 2019 (COVID-19) patients produce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM and IgG. However, the frequency and duration of the antibodies production are not fully understood. Aim and objectives: We aimed to investigate the production of SARS-CoV-2 IgM and IgG over 12 months and to verify the relationship with the characteristics of COVID-19 patients. Method(s): COVID-19 patients admitted to either of Showa University Hospital, Koto Toyosu Hospital, Fujigaoka Hospital, or Northern Yokohama Hospital, were enrolled for the study. The patients were followed up until they became negative for SARS-CoV-2 IgM and IgG or for up to 12 months after the date of SARS-CoV-2 PCR became negative. Result(s): Forty-five patients were enrolled, and 34 patients were followed up to the end. The positivity rates of SARSCoV-2 IgM and IgG were 27.3% and 68.2% when SARS-CoV-2 PCR was negative. The positivity rate of SARS-CoV2 IgG was 70.6%, 52.9%, 14.7%, 2.9% and 0.0% after 1, 3, 6, 9, and 12 months, respectively, after the date of PCR negativity. Moreover, we divided the patients into 2 groups;the milder conditions who did not require oxygen administration (non-severe group) and the severe conditions who required oxygen administration (severe group). The positivity rate of SARS-CoV-2 IgG was significantly higher in severe group compared to non-severe group on the date of PCR negativity and after 1 month, but no significant difference after 3 months. Conclusion(s): Present study suggested that more severe COVID-19 patients produced more SARS-CoV-2 IgG. However, the duration of SARS-CoV-2 IgG production was independent of COVID-19 severity.