Inclusion Criteria:  Adult male or female age equal or more than 20 years with Thai ID cards Received two doses (21-28 days apart) of Sinovac inactivated COVID-19 vaccine who will be divided according to their intervals 60-less than 90 days, 90-less than120 days and 120-180 days Has provided written informed consent prior to performance of any study-specific procedure No history of fever or PUI symptoms within 7 days  Exclusion Criteria:  Any confirmed or suspected immunosuppressive or immunodeficient state. Contraindication to AZ or PF according to labelling of the products History of COVID infection within 3 months period Pregnancy