Objective  To analyze dynamic changes of immunoglobulin M (IgM) and immunoglobulin G (IgG) in 49 confirmed cases of coronavirus disease 2019 (COVID-19) during various periods of the disease and to explore regulations and characteristics of antibodies production against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for providing evidences for effective prevention and control of COVID-19 epidemic.

  Methods  Totally 114 blood samples were collected from 49 viral nucleic acid detection-confirmed COVID-19 patients (one sample for 17 cases and 2 – 7 samples for 32 cases) and blood samples from another 49 viral nucleic acid negative cases were also collected as controls in Changde city, Hunan province between January 24 and February 22, 2020. Fluorescent immunochromatography was used to detect serum SARS-CoV-2 IgM and IgG and dynamic changes in IgM and IgG were statistically analyzed.

  Results  Of the 114 serum specimens from 49 viral nucleic acid positive cases, 96 (84.21%) were IgM positive and 108 (94.74%) were IgG positive, with a significant difference between the two positive rates (P < 0.05). The titer of IgG antibody was significantly higher than that of IgM (P < 0.05) and the titer of IgM was significantly different in the cases at various periods of the disease. The positive rate of IgG varied significantly among the patients at different periods of the disease (P < 0.05). In addition, the results of repeated detection demonstrated that there was a close positive correlation of positive conversion period of IgM and IgG with negative conversion period of viral nucleic acid.

  Conclusion  The detection of IgM and IgG is an effective supplement to the nucleic acid tesing for COVID-19. The dynamic monitoring of SARS-CoV-2 IgM and IgG antibody are of significance for COVID-19-related epidemiological survey, therapeutic effect evaluation, and vaccine development.