Bringing Optimised COVID-19 Vaccine Schedules To ImmunoCompromised Populations (BOOST-IC): an Adaptive Randomised Controlled Clinical Trial

Inclusion Criteria: * Able to give informed consent and undertake study procedures * Age ≥16 years old * Have completed at least 3 months prior, 3- to 8-doses of an Australian TGA approved SARS-CoV-2 vaccine (including mRNA \[Pfizer or Moderna\], ChAdOx1 \[Oxford/Astra Zeneca\] or protein \[Novavax\]) * Fit the criteria to be included in one of the following 3 populations: Infected with HIV; Current recipient of a solid organ transplant including: kidney, pancreas, liver, malignancy episodes of severe rejection requiring T- or B-cell depleting agents in the prior 3 months; Undergoing chemotherapy, immunotherapy and/or targeted therapy, or completed in the last 2 years for: chronic lymphocytic leukemia, multiple myeloma or non-Hodgkin lymphoma. Exclusion Criteria: * Are contraindicated to receive a COVID-19 booster vaccination, e.g. history of anaphylaxis to a vaccine component or myocarditis attributed to previous receipt of an mRNA vaccine. * Has had less than 3 or more than 8 doses of COVID-19 vaccine * Is on another clinical trial investigating alternate COVID-19 vaccination schedules or investigational drugs to prevent or treat COVID-19 * Life expectancy \< 12 months, or enrolment deemed not in the best interest of the patient * Unable to provide informed consent * Receipt of SARS-CoV-2 specific monoclonal antibodies in the 3 months prior to receiving the first dose of study vaccine * Acute respiratory tract infection and/or temperature \> 38 degrees centigrade on day …