Under 65s unlikely to need fourth COVID vaccine dose before winter

Talking points

  • A number of nations including the United Kingdom and United States are rapidly expanding eligibility for a fourth dose, but some experts have questioned its effectiveness.
  • In Australia, a fourth vaccination dose is already recommended for severely immunocompromised people aged over 16, Australians aged over 65, Indigenous Australians aged 50 and over, and residents of aged care or disability care facilities.
  • Infectious disease physician Professor Allen Cheng says there are no immediate plans to implement a fourth dose in Australia’s coronavirus vaccine program more widely.

Australians under 65 years old with no underlying health conditions are unlikely to need a fourth dose of the coronavirus vaccine before winter.

That advice comes from Australian infectious disease experts, who also argue it is too early to make a call on whether further booster shots would be needed before the end of the year.

Otherwise healthy Australians under the age of 65 are unlikely to need a fourth dose of the coronavirus vaccine before winter.Credit:Eddie Jim

But the experts interviewed by The Age and The Sydney Morning Herald say a second booster this year cannot be ruled out entirely, particularly if another more virulent, infectious or vaccine-evasive strain emerges, or if the effectiveness of the third dose is shown to substantially fade over time.

A number of nations, including the United Kingdom and United States, are rapidly expanding eligibility for a fourth dose, but some experts have questioned its effectiveness. The US drug regulator approved a fourth dose for Americans over 50 late last month for anyone who had received their third dose at least four months prior.

In Australia, a fourth vaccination dose is already recommended for severely immunocompromised people aged over 16, Australians aged over 65, Indigenous Australians aged 50 and over, and residents of aged care or disability care facilities.

Asked whether the general population would need a fourth dose before the end of the year, epidemiologist and infectious disease physician Professor Allen Cheng said: “The short answer is we don’t know yet.”

Cheng, a former co-chair of the Australian Technical Advisory Group on Immunisation, said the nation’s chief vaccine advisers were keeping a close eye on any signal that protection against severe disease had waned significantly over time among people who had received a third dose.

While there was mixed data on the lasting effectiveness of a second booster, Cheng said there was strong evidence to suggest that over 65s got better protection from a fourth dose against severe disease.

Cheng said are no immediate plans to implement a fourth dose in Australia’s coronavirus vaccine program more widely.

“For everyone else, even though, what the evidence suggests so far is that giving another dose in the younger people protects them a little bit more, but that effect is probably quite short term,” he said.

“And what the evidence also suggests is that they are still substantially protected by three doses.”

The available data is still preliminary and has not yet shown how long the benefits of a fourth dose will last.

A new study published in The New England Journal of Medicine earlier this year, which examined fourth doses in Israel, found a second booster restores antibodies to levels observed after the third dose, but only provided a modest boost in protection against infection.

The study also found the fourth dose raised participants’ levels of “neutralising antibodies,” which can block viral infection of cells.

Cheng estimates up to 30 per cent of the Australian population have now had coronavirus. He said the bulk of Australians received their third doses in December and January. Despite it being longer than four months since they received their booster, Cheng said they would still have ongoing protection into winter.

But Australian infectious diseases expert Professor Paul Griffin predicts we will all need a fourth dose eventually, perhaps even before the end of the year.

“It is impossible to predict at the moment exactly what that’s going to look like,” Griffin said.

The timing of a broader rollout of fourth doses is dependent on many factors. It could be sped up if a new variant emerges in Australia, or if there is a sudden and concerning wave of infections that sparks a rise in hospitalisations or severe illness.

“At the moment the fourth dose is being recommended for those highest risk groups for very good reason because of their higher risk of severe disease, but also their ability to not respond as strongly to the vaccine so far,” he said.

“But for most of the population, those things don’t hold true and they’re still benefiting from very good protection from a third dose.”

University of Melbourne vaccine expert Fiona Russell also agreed the current available data suggested that three doses was enough for otherwise healthy adults under the age of 65.

“All these decisions are based on monitoring,” Russell said. “At this point there’s no indication that a fourth dose is needed for otherwise healthy people.”

Russell said the fact that millions of Australians had been infected during the Omicron wave would also provide a layer of community protection, known as hybrid immunity, during the winter months. This infection-induced immunity is further boosted by vaccination following a natural infection.

Associate Professor James Trauer, who heads the epidemiological modelling unit at Monash University, said if a fourth dose of the vaccine was to be recommended for the wider population, there should be no further mandating of coronavirus vaccines.

“At some point with the vaccine mandates we’ve really got to say that it’s like three doses is enough to be considered fully vaccinated,” Trauer said.

“We can’t make keep moving the goalposts again and again.”

Trauer says the most important defence at this point in the pandemic is ensuring vulnerable groups with underlying illnesses, and older Australians, get their fourth dose; something he says is already happening.

Israel was the first country to start offering a fourth dose of a COVID-19 vaccine to high-risk populations in December. Chile, Sweden and Germany followed soon after. South Korea is also recommending fourth doses for vulnerable people.

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