Study includes the following four groups of individuals who received both COVID-19 IgM/IgG tests and RT-PCR tests for SARS-CoV-2 from February 29, 2020 to April 29, 2020:

• 1470 hospitalized patients with COVID-19 from Leishenshan Hospital, Zhongnan Hospital of Wuhan University, and Wuhan No. 7 Hospital
• 3832 healthcare providers without COVID-19 diagnosis
• 19555 general workers --1616 other patients to be admitted to the hospital (N=26473)

Mean age was 58.7 years in 1470 COVID-19 patients, 37.1 years in 3832 healthcare providers, 41.6 years in 19555 general workers and 53.3 years in other patients (Table 1). Hospitalized COVID-19 patients were composed of more older people, while healthcare providers and general workers were mostly young adults. Among COVID-19 patients, median time from symptom onset to IgM/IgG test was 41 days (interquartile range 33-50 days). The last RT-PCR tests for SARS-CoV-2 were positive in only eight COVID-19 patients and none of three patients was tested negative for IgG antibodies to SARS-CoV-2.