1. Males or females at least 18 years of age (inclusive) 2. Be subject of study Seroprevalence, Incidence and Immunological Responses to SARS-CoV-2 Infection among Frontline Healthcare Workers compare with Non-COVID-19 HCWs during the COVID-19 Pandemic at Siriraj Hospital, Bangkok or healthcare workers who interested in receiving the vaccine in the study 3. Capable of informed consent and provision of written informed consent before any study procedures

1. Males or females at least 18 years of age (inclusive) 2. Be subject of study Seroprevalence, Incidence and Immunological Responses to SARS-CoV-2 Infection among Frontline Healthcare Workers compare with Non-COVID-19 HCWs during the COVID-19 Pandemic at Siriraj Hospital, Bangkok or healthcare workers who interested in receiving the vaccine in the study 3. Capable of informed consent and provision of written informed consent before any study procedures