inclusion criteria * age 18 and older * all sisonke participants * received a priming ad26.sars.cov.2.s vaccination as part of the sisonke study at least 6 months prior * participants who are pregnant or report breastfeeding at the time of enrolment may be included. * willingness and ability to comply with vaccination plan and other study procedures. * capable of giving electronic or personal signed informed consent as described in appendix 5, which includes compliance with the requirements in this protocol.

inclusion criteria * age 18 and older * all sisonke participants * received a priming ad26.sars.cov.2.s vaccination as part of the sisonke study at least 6 months prior * participants who are pregnant or report breastfeeding at the time of enrolment may be included. * willingness and ability to comply with vaccination plan and other study procedures. * capable of giving electronic or personal signed informed consent as described in appendix 5, which includes compliance with the requirements in this protocol.

inclusion criteria age 18 and older all sisonke participants received a priming ad26.sars.cov.2.s vaccination as part of the sisonke study at least 6 months prior participants who are pregnant or report breastfeeding at the time of enrolment may be included. willingness and ability to comply with vaccination plan and other study procedures. capable of giving electronic or personal signed informed consent as described in appendix 5, which includes compliance with the requirements in this protocol.

inclusion criteria age 18 and older all sisonke participants received a priming ad26.sars.cov.2.s vaccination as part of the sisonke study at least 6 months prior participants who are pregnant or report breastfeeding at the time of enrolment may be included. willingness and ability to comply with vaccination plan and other study procedures. capable of giving electronic or personal signed informed consent as described in appendix 5, which includes compliance with the requirements in this protocol.