A mutant strain of the coronavirus which scientists believe was a precursor to the highly infectious British variant escaped hotel quarantine in Victoria in June during the state's second wave but the public was not told about it at the time.
Professor Damian Purcell, head of the molecular virology laboratory at the Doherty Institute for Infection and Immunity in Melbourne, said the new strain had infected at least 37 people in Victoria before being brought under control by Victoria's lockdown.
This 2020 electron microscope image provided by the National Institute of Allergy and Infectious Diseases – Rocky Mountain Laboratories shows SARS-CoV-2 virus particles which causes COVID-19, isolated from a patient in the U.S., emerging from the surface of cells cultured in a lab.Credit:AP
The information had not been released until now, he said, because “we did not want to spook people that we had a real problem with mutants here”.
“We expect to see them. They are going to keep coming,” Professor Purcell said.
Scientists at the Doherty Institute managed to isolate the variant and have spent several months studying it. Their data suggests that the variant seen in Victoria bound more tightly to human cells, making it harder to contain than the initial strain of SARS-CoV-2.
However, the studies, which are not yet published or peer reviewed, suggest the variant seen in Victoria and others that have since emerged in Britain and South Africa will probably be covered by current vaccines.
The British variant, known as B.1.1.7, emerged in September and appears to sport an unusually large number of changes to its genetic code. A second variant, 501.V2, emerged independently in South Africa at about the same time with similar mutations.
It is not clear how those changes alter the virus, but there is now good evidence the British variant is about 70 per cent more contagious. Less is known about the South African variant.
Eight of the mutations are on B.1.1.7's spike protein, which the virus uses to bind to human cells. Experts suspect some of those mutations allow it to bind tighter to human cells, making it more contagious.
Professor Purcell said 501Y, the virus that escaped Victoria's hotel quarantine, contained several of the mutations seen in B.1.1.7, including changes to the shape of the spike protein.
“Probably the precursor to the British variant was the one we had here in Melbourne,” he said.
Most vaccines target SARS-CoV-2’s spike protein, encouraging the immune system to generate antibodies that can bind to and neutralise it.
Theoretically, big changes to the shape of the spike protein may therefore render vaccines ineffective, explaining why the British and South African variants have prompted global concern.
However, vaccines are designed to generate a range of different antibodies for different parts of the spike. Even if one part of the spike changes shape, the other antibodies should still be effective, according to a number of experts.
Professor Purcell said that in experiments conducted at the Doherty the mutant strain from Victoria had been neutralised by antibodies generated by the University of Queensland’s vaccine as well as vaccines being developed at the Monash Institute of Pharmaceutical Sciences and the institute itself.
Work at the CSIRO has also shown a separate vaccine, made by Inovio, offers protection against the variant, said Professor Trevor Drew, director of the Australian Centre for Disease Preparedness.
Given Pfizer and AstraZeneca’s jabs generated the same antibodies, Professor Purcell said he was confident those vaccines would provide protection. However, his laboratory has not directly tested the strains circulating in Britain or South Africa.
It is possible the extra changes may cut the effectiveness of the vaccine, but probably not to the point where it lost effectiveness altogether, Professor Purcell said.
"We think the level of potency you get with these additional changes will not be enough to allow the virus to escape. We’re quietly confident the vaccines have got this covered."
Leaders of both Pfizer and AstraZeneca have publicly stated they are confident their vaccines will provide protection against the new variants. Tests to find out if that is the case are ongoing.
While Professor Purcell's results are encouraging, lab experiments also show it is possible for the virus to mutate in a way to cut the effectiveness of current vaccines, said Professor Trent Munro, director of the University of Queensland's unsuccessful effort to make a vaccine for COVID-19.
Luckily, new-generation mRNA vaccines offer a potent fix. These vaccines, manufactured by Moderna and Pfizer, contain genetic code allowing the body to make copies of COVID-19’s spike protein and learn how to neutralise it.
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