The COVID-19 pandemic won’t end with a bang, but more likely a fizzle – and a long, protracted one at that.
“I don’t know if we’re going to wake up one day and say, ‘Oh, it’s over now,'” says Eddie Holmes, an evolutionary virologist at the University of Sydney.
“I think what will happen is that gradually, with time, we will think about this disease in a different way.”
Most experts agree that eradicating COVID-19 is now almost certainly out of the question.
Even with sky-high vaccination rates – which, globally, we’re a long way off – it’s unlikely we’ll be able to halt SARS-CoV-2 transmission entirely, University of Queensland virologist Ian Mackay says.
“We’ve got so much virus overwhelming us that most vaccines would struggle to stop infections from happening, no matter how good they are.”
But even in the absence of herd immunity, vaccines considerably reduce severe disease, meaning fewer people will be hospitalised, and fewer still will die.
Over time COVID-19, like other infectious diseases such as the flu, will become endemic – a permanent, albeit more manageable, part of our lives, Professor Holmes says.
“In countries with really high rates of vaccination, the virus is still going to be there,” he said.
“The critical thing, though, is that we massively reduce the burden of disease. That’s what it’s all about.”
Getting from pandemic to endemic
As restrictions begin to lift and Australia transitions to “living with COVID”, case numbers will likely surge, as has been seen in countries such as Singapore and the UK.
Evidence suggests the virus will spread most readily among people who remain unvaccinated, but there will also be cases in vaccinated people, as protection against infection wanes and the proportion of vaccine recipients grows.
“We almost need to not think of the case numbers,” Professor Holmes said.
“It’s the number of people going to hospital that is the key number now.”
Some modelling suggests with a “loose suppression” strategy, states such as NSW and Victoria could record as many as 2,000 new cases per day.
The good news is breakthrough infections tend to be less severe, and most countries experiencing a resurgence in case numbers are seeing a fraction of the hospitalisations and deaths they once did.
There are, however, still people who remain at increased risk, including those who are immunocompromised and elderly, Dr Mackay says.
“We’re still going to see groups of people who will get very sick, because they can’t be vaccinated or their immune system doesn’t respond well.
“Where long COVID plays into all of this is a separate question. Are vaccines protecting against that? I’m not really clear on that yet. I don’t know if anybody is.”
To protect those at risk of severe disease and keep the health system from being overwhelmed, Griffith University virologist and infectious disease researcher Lara Herrero says it’s essential that restrictions are lifted slowly, and certain COVID-safe measures maintained.
“People without immunity being exposed to the virus is the thing we really need to slow down,” she said.
The goal as Australia moves away from a “COVID-zero” approach, she adds, remains as it’s always been: to keep death and disability as low as possible.
“We need to look at this on a community level and say it’s not just about me, it’s about my community,” Dr Herrero said.
Waning immunity and acceptance of risk
Exactly how long it takes to transition to a point where COVID-19 is considered endemic is difficult to say.
The trajectory is likely to vary from country to country, and depend on vaccination rates, population immunity levels (including from infection), and the amount of circulating virus.
While data suggests COVID-19 vaccines provide strong protection against severe disease over time, evidence of waning protection against infection could mean population-wide immunity fluctuates.
Booster vaccine availability and roll-out may become key to shoring up herd immunity.
Professor Holmes says health experts are closely watching highly vaccinated countries such as Denmark, which lifted all restrictions on September 10, to see how case numbers and hospitalisations fare.
“[Denmark] has decided, ‘we are now living with it, it’s just part of our life,'” he said.
“But we need to watch and see whether they’ll still be saying that in six months.”
According to Dr Mackay, the bumpy road to living with COVID-19 will also depend on what governments decide is an acceptable level of disease and death.
“Some people say living with COVID means just ‘letting it go’, with enough vaccinated people to blunt the burden of hospitalisations and deaths,” he said.
“But others want to see a much higher level of protection, to try and stop transmission as well.
“I expect that we’ll probably grow to put up with COVID-19, unless we really change our approach to what we consider acceptable [in terms of] death, disease and economic impact from respiratory viruses.”
What about new variants?
Another factor that will affect how countries manage future COVID-19 threats is the evolution of the virus itself.
With so much of the world still vulnerable to infection – billions of people are yet to receive their first vaccine dose – the virus still has plenty of opportunities to replicate and mutate.
“If you look at the first 18 months of COVID, the variants that were successful were the ones that were most infectious,” Professor Holmes said.
“But as immunity rises — and that’s happening because we’re vaccinating at increasing numbers — the selection pressure on the virus is going to change.”
That change is likely to result in variants that are better able to evade our immune response, he said.
“The question is: if a new variant is able to evade immunity, would it still be as infectious?
“Because there arethese trade-offs [in evolutionary biology] – you can’t actually do everything simultaneously well.”
Professor Holmes said it was possible that future variants would be more transmissible or virulent, but that he thought that was “unlikely”.
“Irrespective of what the virus does, the fact that we all will hopefully get vaccinated … that immune response should dampen subsequent infections, so mortality rates should decline.”
Treating COVID ‘like the flu’
Eventually, though it’s difficult to predict, Professor Holmes says SARS-CoV-2 may start to resemble the seasonal flu.
“My guess is that it will eventually become a winter, seasonal disease in temperate regions … and we will probably get spikes every so often,” he said.
“That corresponds to when the virus has picked up a novel mutation that has allowed it to evade more of the circulating immunity, and we may need a vaccine update when that happens.”
Dr Herrero agrees that endemic SARS-CoV-2 could have seasonal peaks like the flu, but it may have “more severe consequences”.
“We need to continue to monitor the virus as it mutates, so that we don’t end up with another pandemic,” she said.
“Most people don’t realise that every year, the flu vaccine is reviewed and assessed and possibly changed if it needs to be.
“They look at the strains that are circulating, and then they look at the vaccines.”
Dr Mackay says another plausible scenario is that SARS-CoV-2 eventually starts to behave in a similar way to the four other endemic human coronaviruses that cause common colds.
That would likely mean people are first infected in early childhood, exposed multiple times throughout their life, and generally experience only mild symptoms.
“We now have a better idea that kids’ immune systems are really quite protective against a lot of respiratory viruses,” he said.
“They get that first exposure, they become immune, that immunity stays with them for life, and we start the cycle of moderated disease as we grow older.
“What we don’t know is how long that’s going to take.
“It could take six months, it could take years, it could take decades before we actually are comfortable living with this particular virus in that way.”
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