Signed written informed consent Able to follow the vaccination schedules, visits and tests General health or having controlled underlying diseases (based on the physician's diagnosis) Iranian citizenship Residents of Tehran Both sexes (male and female) Aged 18-80 years Receiving the initial 2 doses of Sinopharm within a 28±5 days interval Completion of the 2-dose Sinopharm vaccination course within 3-6 months prior enrollment.

Signed written informed consent Able to follow the vaccination schedules, visits and tests General health or having controlled underlying diseases (based on the physician's diagnosis) Iranian citizenship Residents of Tehran Both sexes (male and female) Aged 18-80 years Receiving the initial 2 doses of Sinopharm within a 28±5 days interval Completion of the 2-dose Sinopharm vaccination course within 3-6 months prior enrollment.