Clinical trials are set to begin on two new COVID-19 vaccines being developed in Melbourne that researchers say may improve immunity to the Omicron variant.
The two vaccines were created by researchers at the Doherty Institute and Monash Institute of Pharmaceutical Sciences (MIPS).
The trials will assess the effectiveness of the vaccines as a fourth dose, and will involve people who have already had three doses of a vaccine.
Researchers said the jabs were distinct from existing vaccines as they targeted the tip of the virus spike protein, known as the receptor binding domain (RBD).
The RBD protein vaccine uses part of the virus protein to elicit an immune response, and the RBD mRNA vaccine uses the genetic sequence of the virus.
University of Melbourne researcher Georgia Deliyannis, who conducted most of the RBD protein vaccine experiments at the Doherty Institute, said the vaccine induced a high level of antibodies in pre-clinical trials.
"Immunity induced by the RBD protein vaccine protects against virus challenge in a mouse model of SARS-CoV-2 infection, even 100 days following the boost," Dr Deliyannis said.
"As well as inducing strong neutralising antibody immunity to the Beta variant in mice, it also retains its potential to neutralise the original ancestral strain, and preliminary in-lab studies have demonstrated neutralising activity against other variants including Delta and Omicron."
Colin Pouton from MIPS, who led development of the RBD mRNA vaccine, said researchers were confident of successful clinical trials.
"In common with the RBD protein vaccine, the RBD mRNA vaccine induced high levels of RBD-specific antibodies and protected against virus challenge in the mouse model," Professor Pouton said.
If the clinical trials prove successful, the candidates would be the first COVID-19 vaccines to be developed entirely within Australia.
Sharon Lewin from the Doherty Institute said there would continue to be a great demand for COVID-19 vaccine options.
"Both vaccines are efficient to produce and can be rapidly modified to incorporate distinct or multiple RBD mutations arising in future variants," Professor Lewin said.
"In addition, Australia needs the ability to manufacture its own vaccines to ensure our own supply should future global shortages occur, and to contribute to the global need for COVID-19 vaccines."
