- The country’s top vaccine advisory group may hold off advising more Australians to get their fourth COVID shot until better, Omicron-specific vaccines are available.
- The group is closely watching the United States where Moderna will soon file clinical data on its updated Omicron-specific booster to the drug regulator.
- Omicron sub-variants, including BA.4 and BA.5, are fast becoming the dominant variants in Australia and there is growing concern the sublineages are becoming more effective at reinfecting people.
- Professor Tony Cunningham, an infectious disease physician, says variant-specific booster shots are the future of coronavirus vaccines and may be adjusted just like seasonal flu jabs.
- Australians aged over 65, Aboriginal and Torres Strait Islanders over 50 and Australians under 64 who are immunocompromised, are already advised to get their fourth booster shot.
Australia’s vaccine advisory panel is considering delaying a recommendation that more people get a fourth COVID booster shot until a better Omicron-targeting vaccine is available.
Omicron sub-variants, including BA.4 and BA.5, are fast becoming the dominant COVID-19 variants in Australia and there is growing concern the sublineages are becoming more effective at reinfecting people.
Moderna released preliminary results earlier this month on an updated coronavirus vaccine that targets Omicron.Credit:Alex Ellinghausen
Professor Allen Cheng, who is a voting member and the former chair of the Australian Technical Advisory Group on Immunisation, said the expert group was watching the United States closely, where Moderna will imminently file clinical data on its Omicron-containing bivalent booster to the drug regulator.
“One of the big considerations we are looking at is, do we recommend the fourth dose more broadly in Australia, knowing that there might be a better fourth dose to get down the line?” he said.
Cheng said the expert panel had no immediate changes to the advice on fourth doses in Australia, adding three doses still appeared to provide ongoing protection against severe disease for those under the age of 65, who were otherwise healthy.
“Do we recommend the fourth dose more broadly in Australia, knowing that there might be a better fourth dose to get down the line?”
But the respected infectious disease physician said there were many complexities being considered in Australia, including the benefits of fast-tracking a fourth dose of the current vaccines against the risks, and determining what the alternatives could be.
“The alternatives are that maybe there will be a better variant vaccine and if we just wait a few months longer we will have access to that in Australia,” he said.
Moderna released preliminary results earlier this month on its updated coronavirus vaccine, after the company’s researchers tested a booster dose, combining the spike protein of the ancestral SARS-CoV-2 virus that originated in Wuhan with one specifically targeting Omicron’s BA.1 variant.
The combination produced 1.75 times the level of neutralising antibodies against Omicron as the existing Moderna vaccine, the company said. These results, while promising, are yet to be scrutinised through peer reviewing.
If Moderna’s booster is approved for use in the US as predicted, the company’s chief medical officer Dr Paul Burton said it was poised to deploy the booster quickly to “as many people around the world as possible”.
Pharmaceutical giant Pfizer is also creating an updated booster, which it said would be better at fending off Omicron.
Paul Griffin, an infectious diseases expert who has been the principal investigator for seven COVID-19 vaccine clinical trials, said the evidence around fourth doses for younger people with no risk factors for serious disease, still remained unclear.
“At the moment, there remains no convincing evidence for people who don’t have risk factors to urgently get that fourth dose,” he said.
But this could change quickly. Griffin said the new Omicron sub-variants were displaying partial immune evasion to existing vaccines, leading to people getting reinfected more readily – even if they had had their third dose or been infected with coronavirus recently.
Professor Allen Cheng said Australia’s vaccine advisory group was closely watching the US, where Moderna will soon file new clinical data.Credit:Simon Schluter
This is because genetic mutations in the spike protein of subvariants BA.4 and BA.5 allow them to evade the immune system’s radar and some antibodies we might have made against other variants.
“There are concerning signs this is leading to an increase in severity and an increase in hospitalisations globally,” Griffin said.
In the UK coronavirus hospitalisations are rising sharply again. Griffin said there are early signs this trend in severity may already be happening in NSW.
“This is about the continual evolution of the virus and the increasing challenges it poses.”
“A fourth dose of an Omicron-specific booster may be needed in the not too distant future,” he said. “It is increasingly looking like this might be the case.”
Professor Tony Cunningham, an infectious disease physician at the Westmead Institute for Medical Research, said the crucial question was: what is likely to happen with new variants, such as BA.5, and our antibody levels over the next few months?
“My bet will be that it will decline enough that we will need to give a fourth dose,” Cunningham said.
Asked about waning immunity for people who had received their third dose at the end of last year, Cunningham said data from Israel had shown there was stable protection against severe disease for up to five months. His view was that a variant-specific fourth dose may be needed beyond six months, particularly for high-risk groups such as healthcare and aged care workers.
According to a large new study from Israel, a fourth shot of the Pfizer vaccine provides additional short-term protection against Omicron infections and severe illness among older adults. But it wanes after just four weeks.
Griffin said variant-specific boosters were the future of coronavirus vaccines and could be adjusted just like seasonal flu jabs.
But he warned fatigue and scepticism about booster shots must be overcome with careful and considered health messaging.
“A lot of people think the need for boosters suggests we got things wrong at the start,” he said. “But the fact is the vaccines do work. This is about the continual evolution of the virus and the increasing challenges it poses.”
A fourth dose is currently available to anyone aged over 65, Aboriginal and Torres Strait Islanders over 50 and Australians under 64 who are immunocompromised.
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