inclusion criteria: 1. have completed two doses of pfizer-biontech or astrazeneca vaccines with the recommended schedule 6 months prior to the date of enrolment 2. willing and able to give written informed consent 3. aged 18 years or above 4. willing to complete the follow-up requirements of the study

inclusion criteria: 1. have completed two doses of pfizer-biontech or astrazeneca vaccines with the recommended schedule 6 months prior to the date of enrolment 2. willing and able to give written informed consent 3. aged 18 years or above 4. willing to complete the follow-up requirements of the study

inclusion criteria: have completed two doses of pfizer-biontech or astrazeneca vaccines with the recommended schedule 6 months prior to the date of enrolment willing and able to give written informed consent aged 18 years or above willing to complete the follow-up requirements of the study

inclusion criteria: have completed two doses of pfizer-biontech or astrazeneca vaccines with the recommended schedule 6 months prior to the date of enrolment willing and able to give written informed consent aged 18 years or above willing to complete the follow-up requirements of the study