Two Melbourne-made COVID-19 vaccines have shown strong potential to be an improved approach for boosting immunity to SARS-CoV-2 variants, according to interim results of a Phase 1 clinical trial published in eBioMedicine.
The trial involved 76 healthy adults in Melbourne, aged 18 to 64, who had previously received licensed SARS-CoV-2 vaccines. These individuals were randomized to receive a fourth dose of a novel protein vaccine, an mRNA vaccine, or a placebo.
Both vaccines demonstrated strong boosting capabilities in a highly immune population and a remarkable breadth of immune response, including against omicron sub-variants. Importantly, no safety signals were observed with either vaccine candidate.
The two vaccine candidates, developed by researchers at the Peter Doherty Institute for Infection and Immunity and the Monash Institute of Pharmaceutical Sciences, are distinct from most existing vaccines because they focus the immune response on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein.
The RBD is crucial for the virus to enter and infect cells, eliciting over 90 percent of neutralizing antibodies that can block the virus.
The two candidates are:
- RBD protein vaccine: This vaccine uses an engineered part of the virus protein, rather than genetic material or another virus, to stimulate an immune response.
- RBD mRNA vaccine: This vaccine represents the virus’s genetic sequence of mRNA that codes for the tip of the spike protein, leading to the production of the RBD protein in the recipient.
Professor Terry Nolan, Head of the Vaccine and Immunization Research Group at the Doherty Institute, expressed great satisfaction with the trial results.
He emphasized that these vaccines, which focus on the RBD, could offer a more efficient approach to boosting immunity to the virus and should proceed to Phase 2 clinical trials.
Professor Colin Pouton of the Monash Institute of Pharmaceutical Sciences, who led the development of the RBD mRNA vaccine, highlighted its strong immune response, even at low doses.
These vaccines can potentially address issues related to COVID-19 variant vaccines, reduce death rates, and potentially provide protection against emerging variants.
The research team is exploring options for advancing these vaccines to Phase 2 trials.
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The research findings can be found in eBioMedicine.
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