CD40LG and COVID-19: In addition, the positive rate was higher in COVID-19 RPs who had severe or critical illness (IgG-positive, 96.7%; IgM positive, 15.4%) than in those who had suffered from mild/moderate illness (86.0 and 6.0%, respectively) or who were asymptomatic (85.2 and 7.4%, respectively), indicating that the more serious the condition, the longer the antibodies might linger in RPs.