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There are no immediate plans to implement a fourth dose in Australia’s coronavirus vaccine program, with the country’s top vaccine advisory group warning it was too premature to determine if a second booster will be needed to halt the spread of the fast-moving Omicron variant.
But Professor Allen Cheng, who sits on Australian Technical Advisory Group on Immunisation, said the need for a second booster later this year could not be ruled out, especially if a more infectious, virulent and vaccine-evasive strain emerged or if Omicron continued to push healthcare systems to the brink.
Professor Allen ChengCredit:Joe Armao
Debate around the need for a fourth dose of the vaccine is mounting globally after Israel broke ranks with the rest of the world and began rolling out a second booster to all healthcare workers and people aged over 60. To date, more than 450,000 Israelis have received their fourth dose.
This week, Denmark became the first European country to endorse a fourth dose for people at risk of serious illness with the virus, while Chile started rolling out fourth doses to higher-risk members of its population Monday.
In Australia, a fourth dose is already recommended for people with compromised immune systems.
Professor Cheng said the nation’s chief vaccine advisers were also weighing up whether a COVID-19 vaccine, that specifically targets the highly mutated Omicron variant, will be needed in Australia to stem an outbreak currently infecting tens of thousands of people a day.
One such vaccine is being made by pharmaceutical giant Pfizer and is set to made available from March.
“All of this is on the table,” the infectious disease physician and epidemiologist said. “But it is too early to make the call yet. We need to wait for the data.”
Some scientists cautioned against the move, concerned too many shots in a short space of time might actually harm the body’s ability to fight the COVID-19 virus by causing a type of immune system fatigue.
The European Union’s drug regulator also expressed doubts, arguing there is currently no evidence to support a fourth-dose approach.
Professor Cheng said data from Israel on the efficacy of a fourth dose for the older population and healthcare workers will be crucial in the coming months and form the expert panel’s decision on whether such measures are needed in Australia.
University of Melbourne vaccine expert and epidemiologist Fiona Russell said it was too soon to be considering a fourth dose, with evidence suggesting three doses were about 90 per cent effective in preventing severe disease with Omicron.
“Over time, we will see what happens with waning immunity, but certainly, right now, this should not even be considered,” she said.
Instead, Professor Russell said the priority must be on speeding up booster shots for people in aged care, who are among the highest risk of severe disease, after the booster program for the elderly slowed dramatically over the Christmas/New Year break ahead of an explosion of infections.
“This is absolutely critical,” she said.
On Christmas Eve, the interval between the second and third vaccination doses was slashed from five to four months in Australia as Omicron spread.
Tony Cunningham, director of the Centre for Virus Research at the University of Sydney and one of the country’s leading vaccine experts, said a fifth dose may be required for immunocompromised people amid mounting concern organ transplant recipients and those with blood cancers responded poorly to the vaccine.
There is an early suggestion their protection against the virus wanes quickly, even after a third dose.
“It is indeed possible that we may need fifth boosters for the immune-compromised group,” Professor Cunningham said.
Some experts have signalled a winter booster will be needed for those aged over 60, the vast majority of whom will receive their booster at the beginning of the year.
Professor Cunningham said while very early Israel data indicated a winter booster might be needed for the elderly, much more evidence was needed.
“Right now, there are just too many unanswered questions about the long-term protection of the third dose,” he said.
But he said as Omicron rages, the next variant awaits, and we must prepare our vaccines accordingly.
“People saying this is the last variant we are going to get are unwise,” Professor Cunningham said.
Paul Griffin, an infectious diseases expert who has been the principal investigator for seven COVID-19 vaccine clinical trials, remains unconvinced a winter booster will be needed in Australia.
“It is looking more and more like protection with one booster shot will be sufficient for Omicron,” he said.
Like Professor Cheng, he said this could change quickly if another vaccine-evasive variant emerged.
And if cases of Omicron continue to rise exponentially in Australia, a variant-specific vaccine may be needed to slow down transmission, Professor Russell said.
“We know our current vaccines are good against severe disease, but they are not so good against transmission and if we still have large amounts of infection in a couple of months, this has to be considered,” she said. “Omicron might come and go quickly, but it is not going to disappear.”
Into the future, Professor Griffin predicts a combined coronavirus and influenza shot will be used to protect Australians. Several studies are under way to test the safety and efficacy of combining the vaccines.
Moderna is one of several drug companies developing a single vaccine that combines a booster dose against COVID-19 with its experimental flu shot.
“It might even be that it has protection against two or three variants in the coronavirus part of the vaccine and the usual quadrivalent flu vaccine, so people will get protected against the variants of both circulating at that point in time,” Professor Griffin said.
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