Two Australian-made Covid-19 vaccines entering clinical trials

SYDNEY (XINHUA) - Two new Australian-made Covid-19 vaccines will enter trials with hopes that they may provide more targeted protection against the virus.

The two vaccine candidates, unveiled on Friday, were created by researchers at the Peter Doherty Institute for Infection and Immunity and the Monash Institute of Pharmaceutical Sciences (MIPS), with 114 eligible Australians to be recruited to participate in the first-in-human trial.

Both vaccines are distinct from existing vaccines, because they focus the immune response on the tip of the SARS-CoV-2 spike protein, called the receptor binding domain (RBD).

"The RBD enables the virus to enter and infect cells in the body and elicits over 90 per cent of neutralising antibodies (antibodies that can block the virus) following SARS-CoV-2 infection," the Peter Doherty Institute explained in a statement on Friday (March 25).

While both vaccines target the RBD of SARS-CoV-2, they use different technologies.

The first, RBD protein vaccine, is a traditional recombinant protein vaccine, and works by creating an immune response to proteins in the virus.

The other, RBD mRNA vaccine, used the genetic sequence of the tip of the spike, rather than the protein itself.

Vaccine developers said, in pre-clinical trials, both vaccines showed high levels of RBD-specific antibodies in mice, and they can be rapidly modified to incorporate multiple RBD mutations.

"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," said Professor Colin Pouton of MIPS, who led the development of the RBD mRNA vaccine.

Dr Georgia Deliyannis, who performed most of the RBD protein vaccine experiments at the Peter Doherty Institute, also said immunity induced by the RBD protein vaccine protects against the virus in a mouse model of SARS-CoV-2 infection even 100 days following the boost.

"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," Dr Deliyannis said.

The phase-1 clinical trial will assess the safety and efficacy of a single dose of both vaccines as a fourth dose of the Covid-19 vaccine.

All participants are required to have had their third dose at least three months before the study commenced.