- Males or females at least 18 years of age (inclusive) - Have received 2nd dose of COVID-19 vaccine (CoronaVac or ChAdOx1) for 8-12 weeks earlier - Can understand Thai language through speaking, reading and writing - Able to communicate through electronic tools such as Google form or line - Capable of attending all study visits according to the study schedule - Capable of informed consent and provision of written informed consent before any study procedures

- Males or females at least 18 years of age (inclusive) - Have received 2nd dose of COVID-19 vaccine (CoronaVac or ChAdOx1) for 8-12 weeks earlier - Can understand Thai language through speaking, reading and writing - Able to communicate through electronic tools such as Google form or line - Capable of attending all study visits according to the study schedule - Capable of informed consent and provision of written informed consent before any study procedures

- Males or females at least 18 years of age (inclusive) - Have received 2nd dose of COVID-19 vaccine for 12 to 20 weeks - Can understand Thai language through speaking, reading and writing - Able to communicate through electronic tools such as Google form or line - Capable of attending all study visits according to the study schedule - Capable of informed consent and provision of written informed consent before any study procedures

- Males or females at least 18 years of age (inclusive) - Have received 2nd dose of COVID-19 vaccine for 12 to 20 weeks - Can understand Thai language through speaking, reading and writing - Able to communicate through electronic tools such as Google form or line - Capable of attending all study visits according to the study schedule - Capable of informed consent and provision of written informed consent before any study procedures