This supplementary appendix, part of the original submission and peer-reviewed, includes additional data and analyses from the study. It provides detailed information on the Oxford Trial Group List, acknowledgements, and various tables and figures that supplement the main findings of the study. The tables cover baseline characteristics, follow-up times, hospitalization rates, factors influencing booster dose receipt, vaccine efficacy, and adverse events. The figures illustrate vaccine efficacy against asymptomatic/unknown infections, neutralizing antibody responses, and cumulative incidence of primary symptomatic PCR+ cases after the booster dose. The appendix also includes data on unsolicited adverse events and their severity grades.This supplementary appendix, part of the original submission and peer-reviewed, includes additional data and analyses from the study. It provides detailed information on the Oxford Trial Group List, acknowledgements, and various tables and figures that supplement the main findings of the study. The tables cover baseline characteristics, follow-up times, hospitalization rates, factors influencing booster dose receipt, vaccine efficacy, and adverse events. The figures illustrate vaccine efficacy against asymptomatic/unknown infections, neutralizing antibody responses, and cumulative incidence of primary symptomatic PCR+ cases after the booster dose. The appendix also includes data on unsolicited adverse events and their severity grades.