Safety and Immune Response of Adjuvanted SARS-CoV-2 (COVID-19) Beta Variant RBD Recombinant Protein (DoCo-Pro-RBD-1 + MF59®) and mRNA (MIPSCo-mRNA-RBD-1) Vaccines in Healthy Adults

This is a study of two experimental SARS-CoV-2 vaccines against the virus called SARS-CoV-2 virus. The first of the experimental vaccines is called DoCo-Pro-RBD-1 + M59® and contains a laboratory made protein which looks the same as a protein in the SARS-CoV-2 virus. As this protein is so similar to a protein in the SARS-CoV-2 virus, it allows the immune system to develop immunity against the real virus by producing specific antibodies against this protein. Antibodies are substances in the blood which could help protect against future infection. The second of the experimental vaccines that will be tested is called MIPSCo-mRNA-RBD-1. This type of vaccine uses messenger ribonucleic acid (mRNA) which is a set of instructions for a cell to make a viral protein called an antigen. Antigens are substances that can trigger the body's defences to produce antibodies that fight against the disease. This study will test these two experimental COVID-19 vaccines in people who have previously received two doses of ComirnatyTM (Pfizer Australia Pty Ltd) or VaxzevriaTM (AstraZeneca Pty Ltd) and a third booster vaccination with either ComirnatyTM or SpikevaxTM (Moderna). This study is the first time this recombinant protein vaccine and this mRNA vaccine will be given to humans. The purpose of this study is to determine what amount, or dose, of the experimental vaccines is safe and produces the desired immune response and antibody level for future investigations. It will do this by testing 3 different dose levels for each of the two vaccines. Each participant will receive a single vaccine at one of the three dose levels, or a placebo injection. This study is the first time this recombinant protein vaccine and this mRNA vaccine will be given to humans.