COVID vaccine candidate protects against multiple variants

A new COVID-19 vaccine candidate, developed by researchers at the Centenary Institute and The University of Sydney, has shown strong potential to protect against both current and emerging coronavirus variants.

By targeting features shared by a range of coronaviruses, the vaccine is designed to offer broader and longer-lasting protection as the virus continues to evolve. The work was funded by the Coalition for Epidemic Preparedness Innovations (CEPI) and has been described in the journal npj Vaccines.

The vaccine candidate, named CoVEXS5, features a unique version of the spike protein, which fuses protein elements from several coronaviruses into a single structure. This fusion helps the immune system recognise and respond to a broader range of virus types, not just one specific strain.

“By combining parts of multiple coronaviruses, we’ve created a vaccine that can better prepare the body to fight off both current and future threats,” said Centenary researcher Dr Claudio Counoupas, co-lead author on the team’s study.

The study showed that CoVEXS5 protected mice from multiple coronaviruses, including the highly immune-evasive Omicron XBB.1.5 variant and SARS-CoV-1, a relative of SARS-CoV-2 that was responsible for the 2002–2004 SARS outbreak. In laboratory tests, it reduced virus levels in the lungs of infected mice by approximately 99.9% compared to unvaccinated controls, demonstrating a dramatic protective effect.

Notably, the vaccine candidate triggered high levels of virus-blocking antibodies and activated special immune T cells in the lungs that play a key role in defending against respiratory viruses. Co-lead author Elizabeth Chan, a PhD student at the Centenary Institute and The University of Sydney, said the findings highlight the potential for a next-generation COVID-19 vaccine that could work across different variants.

“The immune response we saw in the laboratory was both strong and broad,” Chan said. “It’s exciting to think that this approach could help futureproof vaccines against ongoing changes in the virus.”

The vaccine candidate also includes Sepivac SWE, an open-access adjuvant that enhances the immune response and offers practical advantages for vaccine manufacturing and global distribution.

“Sepivac SWE is not only effective, but because it’s open-access, it can be used by manufacturers around the world without licensing barriers or high costs,” said senior study author Professor Jamie Triccas, Deputy Director of the Sydney Infectious Diseases Institute at The University of Sydney.

“That’s a huge advantage for global vaccine equity, especially in low- and middle-income countries where access and cost are critical concerns.”

The research team is now focused on advancing the vaccine candidate through further development and testing.

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