‘We need new antivirals’: Australia’s ‘Omicron soup’ is blunting our best COVID treatments

Infectious diseases experts are warning that almost all available antiviral medications are increasingly ineffective against the “soup” of Omicron descendants now circulating in Australia.

It has escalated the urgency for advancements in the medications needed to protect those most vulnerable to severe disease and death from COVID-19.

Antiviral treatments available in Australia are becoming are increasingly ineffective against current strains of Omicron circulating.Credit:AP

Professor Stuart Turville, a virologist at the Kirby Institute, said many of Australia’s best treatments were no longer effective against XBF, the dominant subvariant in Victoria, accounting for about a third of all infections, and BQ.1.1, which is also circulating widely.

Experts say full vaccination and being up-to-date with booster shots still provides significant protection. But monoclonal antibody drugs including Sotrovimab and Evusheld, which are delivered intravenously, are particularly important for severely immunocompromised patients or people who cannot get vaccinated.

New research undertaken by the Kirby Institute found Evusheld was ineffective against all variants tested, while Sotrovimab still provided some protection against most of the variants in circulation, but at a lower level of effectiveness than earlier coronavirus variants.

Paxlovid, an oral antiviral medication available in Australia, still remains effective against all the subvariants.

“The bottom line is we need new antivirals,” Professor Tony Cunningham, an infectious diseases physician at the Westmead Institute for Medical Research, said.

“Resistance to Paxlovid would be disastrous.”

The immunologist said experts were also weighing up whether a longer duration of antiviral treatment with Paxlovid may be required, amid evidence patients’ symptoms can rebound if treatment is stopped, while the virus remains in the upper respiratory tract.

Monoclonal antibody treatments are laboratory-made proteins designed to mimic the natural antibodies produced by the immune system, stopping the virus from replicating.

Turville, who led the study on the ability of approved monoclonal antibody therapies to neutralise variants, said Australia’s mix of newer strains had made treating severe COVID-19 more challenging, with fewer effective drugs in the “therapeutic cupboard”.

He said the research showed how important it was for Australia to focus on advancing antiviral treatments for those most at risk of severe disease.

Turville said work was being undertaken across Australia to enhance treatments for coronavirus. A clinical trial at the Kirby Institute is examining the effects of a protease inhibitor – the type of antiretroviral drug used to treat HIV – developed by a Japanese company.

Doherty Institute director Professor Sharon Lewin is also leading a team working on new antivirals to prevent and treat coronavirus.

University of Queensland virologist Dr Kirsty Short said she was most concerned about Australians missing out on antivirals or being given them too late due to the reliance on rapid antigen tests, which are not always effective.

“To be most effective, antiviral medication should be given as soon as possible after symptoms from COVID,” Short said. “So we need a better way of diagnosing people earlier in the infection.”

Under guidelines for Australia’s Therapeutic Goods Administration, rapid antigen tests must be at least 80 per cent effective.

Short said to manage coronavirus in the future, Australia needed to revolutionise how people are being screened for the disease.

She said emerging technology, including new RNA at-home point-of-care tests, showed signs of being more effective at detecting coronavirus than regular rapid antigen tests. Research suggests the tests may soon be able to detect genetic material, similar to a PCR test.

“The problem is the technology is not widely available and is expensive, so we need to increase access,” she said.

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