Results
Of participants who consented to this sub-study, 874 completed COVID-19 vaccination courses before 9th August 2021 and provided post-vaccination blood samples (Participant flow chart. Participants in the BRACE COVID-19-Specfic vaccine (BCOS) sub-study were a subset of participants from the BRACE trial. BRACE trial participants in Brazil who received (or were due to receive) two doses of COVID-19-specific vaccines prior to August 9