inclusion criteria: * adults of 18 years old and above. * participants who are at high risk of sars-cov-2 infection. * able and willing (in the investigator's opinion) to comply with all study requirements. * willing to allow the investigators to discuss the volunteer's medical history with their general practitioner/personal doctor and access all medical records when relevant to study procedures. * agreement to refrain from blood donation during the study. * provide written informed consent.

inclusion criteria: * adults of 18 years old and above. * participants who are at high risk of sars-cov-2 infection. * able and willing (in the investigator's opinion) to comply with all study requirements. * willing to allow the investigators to discuss the volunteer's medical history with their general practitioner/personal doctor and access all medical records when relevant to study procedures. * agreement to refrain from blood donation during the study. * provide written informed consent.

inclusion criteria: - adults of 18 years old and above. - participants who are at high risk of sars-cov-2 infection. - able and willing (in the investigator's opinion) to comply with all study requirements. - willing to allow the investigators to discuss the volunteer's medical history with their general practitioner/personal doctor and access all medical records when relevant to study procedures. - agreement to refrain from blood donation during the study. - provide written informed consent.

inclusion criteria: - adults of 18 years old and above. - participants who are at high risk of sars-cov-2 infection. - able and willing (in the investigator's opinion) to comply with all study requirements. - willing to allow the investigators to discuss the volunteer's medical history with their general practitioner/personal doctor and access all medical records when relevant to study procedures. - agreement to refrain from blood donation during the study. - provide written informed consent.