This study aimed to determine the
IgM and
IgG responses against severe acute respiratory syndrome coronavirus (SARS-CoV)-2 in
coronavirus disease 2019 (COVID-19) patients with varying illness severities.
METHODS:
IgM levels increased during the first week after
SARS-CoV-2 infection, peaked 2 weeks and then reduced to near-background levels in most patients.
IgG was detectable after 1 week and was maintained at a high level for a long period. The positive rates of
IgM and/or
IgG antibody detections were not significantly different among the mild, severe and critical disease groups. Severe and critical cases had higher
IgM levels than mild cases, whereas the
IgG level in critical cases was lower than those in both mild and severe cases. This might be because of the high disease activity and/or a compromised immune response in critical cases. The
IgM antibody levels were slightly higher in deceased patients than recovered patients, but
IgG levels in these groups did not significantly differ. A longitudinal detection of
antibodies revealed that
IgM levels decreased rapidly in recovered patients, whereas in deceased cases, either
IgM levels remained high or both
IgM and
IgG were undetectable during the disease course.
CONCLUSION: