Letting Omicron into Australia at high levels – a wise move or heresy? | Tony Blakely



Public discourse about Omicron is largely focused on the next few weeks. To work out what is best to do now, it helps to also think about the next six months to a year.

In broad-brush terms, there are two pathways out of this pandemic. First, we continue to suppress the virus to low levels, and wait for better vaccines. Maybe by mid-2022 we will have new vaccines that are much better than current one against Omicron (and future variants), and not only protect against serious illness but also greatly reduce the chance of any infection. And it is game-back-on to try to achieve that illusive herd immunity through vaccination alone.

But to achieve herd immunity through new improved vaccines alone is a big ask. Omicron is more infectious than Delta, meaning it would take a near 100% vaccine efficacy at stopping any infection (Pfizer is 80%, AstraZeneca is 60%) with no waning (both Pfizer and AstraZeneca immunity against any infection wanes over time). While I would be delighted if such vaccines arrive, I suspect it unlikely in the next six months.

The second general pathway out of this pandemic is a messier one – using both vaccines and natural infection to get to something like herd immunity. A study from Israel found that an infection with a pre-Delta variant was 13 times better than two doses of Pfizer at preventing a Delta infection. Other evidence finds that natural infection is better than vaccines at inducing the sort of immune response that is better at stopping upper airways infection – which is what matters for stopping transmission and getting (close) to herd immunity.

Could letting Omicron in at levels high enough to generate a meaningful contribution to building up our resilience and immunity be a wise move? This option harks right back to the beginning of the pandemic, when we talked about flattening the curve.

Flattening the curve with Omicron would look like allowing the daily infections in a given state or jurisdiction to get up to the level where hospitalisation caseload is manageable. For Victoria and New South Wales, that might be about 1,000 to 2,000 people in hospital at any point in time – which with Delta and current vaccination levels occurs at about 2,000 to 5,000 cases a day. With Omicron we do not know what this ratio is yet – but it might well be about 10,000 cases a day, given that it is likely to be less severe (although exactly how less severe we do not yet know). Thankfully, it does appear that the length of hospital stay is shorter, which will help reduce the stress on the health system.

At, for arguments sake, an average of 20,000 infections a day (which will be more than the daily reported cases, due to asymptomatic and unreported infections) that would be about 2m infections over four months. Or about a quarter of the population of NSW or Victoria.

Is allowing about 2 million people to be infected with Omicron heresy? There would be mortality and morbidity but the tradeoff is getting to a place in the second half of 2022 where we are more resilient to whatever the next variant is.

We do not need to make this choice between keeping infection levels low to mid-2022, or letting them run high, until January or February. In the meantime, we need to boost everyone (especially elderly Australians). In January we should have better data on just how virulent Omicron is, and hopefully clearer signals on what vaccines are realistically coming by mid-2022 – then we should decide which path.

In the next month we will see marked variation across Australasia in the short-term strategies. South Australia, Tasmania, the Northern Territory and New Zealand are unlikely to want to let infection levels get high, and will use strengthened public health and social measures to keep the lid on infections as soon as Omicron gets in. Victoria and NSW may be more prepared to let cases go up to 10,000 or so a day but they will also still need to use strengthened public health and social measures to stop the infection rate breaking through this high limit as vaccination alone (even with boosters) is unlikely to keep a lid on it. But if a state runs high infection rates, over time the necessary intensity of public health and social measures will diminish as immunity from natural infection increases.

Regardless of where you live in Australasia, and what level of infection your jurisdiction explicitly or implicitly decides to try to live with, strengthened public health and social measures will be needed – for a period of time at least.

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