Figure 1.

The positivity of each antibody test kit at various time points after the onset reveals distinct seroconversion. The number of tested patients and days after the onset are shown. Black columns indicate patients with positive results while white columns indicate patients with negative results. For 10 symptomatic patients, the onset date was defined as the date on which symptoms or chest imaging findings compatible with COVID-19 appeared. For two asymptomatic patients lacking significant chest imaging findings, the onset date was defined as the date on which RT-PCR positivity was confirmed.