CD40LG and COVID-19: As for subgroups, the positive rate of IgM was at a higher level in the COVID-19 convalescent group (mean ± SE: 33.41 ± 0.34) compared to the SSC [Screening for symptomatic condition (the most common symptoms related to COVID-19 including fever, cough, chest tightness, diarrhea)] group (mean ± SE: 4.41 ± 0.09) and the SAC [screening for asymptomatic conditions (health examination professionals who were asymptomatic currently, but did not rule out close contacts or had a symptom related to COVID-19)] group (mean ± SE: 1.28 ± 0.09) (Fig. 1B).