Inclusion Criteria:  Working at the CDC Between the ages of 18 and 59 Healthy Not vaccinated with COVID-19 vaccine Agreed to take a blood sample  Exclusion Criteria:  who cannot take the COVID-19 vaccine due to some personal reasons history of SARS-CoV, SARS-CoV-2, or Middle East respiratory syndrome infection high-risk epidemiology history within 14 days before enrolment (eg, travel or residence history in communities with case reports, or contact history with someone infected with SARS-CoV-2) axillary temperature of more than 37·0℃ history of allergy to any vaccine component.