Home Immunity Against a burgeoning immune evasionist Omicron, boosters and masks are Australia’s best weapons | Catherine Bennett

Against a burgeoning immune evasionist Omicron, boosters and masks are Australia’s best weapons | Catherine Bennett

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Living with Covid has taken on a whole new meaning in 2022.

We had been prepared for the virus to stay in our communities, but Omicron took that to a different level. This is what “vaccine escape” looks like.

As we watched the Delta outbreaks in NSW and Victoria slowly come under control in 2021 with more people completing our primary vaccination cycle, we had every reason to be optimistic about some relief. during the summer, even with the international and open state borders.

But that was wiped out with the arrival of Omicron even before the end of the year.

Omicron took off in South Africa, where it was first reported, then gradually circled the globe, culminating in Australia on January 14 this year. It was oddly able to quickly establish vast waves wherever it landed, and not just because it was inherently better at spreading. It is more effective due to its ability to evade our immunity.

Neither previous infection nor vaccination offers much protection against infection with this variant. It’s immune evasion, which comes from the fact that it’s physically different enough from other variants that our immune system doesn’t immediately recognize it to mount an attack, and Omicron represents a bigger change than the one we we saw in the previous immune leak with Delta – so much so that some argue that Omicron should not be lumped together with the other Sars-CoV-2 variants seen in this pandemic at all.

Immune evasion undermines the immune system’s ability to ward off infection, but luckily we still have enough cross-immunity against vaccination, infection, or both to reduce our risk of serious illness. During the peak last January, we had more than 50 times the infections reported in the Delta wave, but only a third more people in intensive care.

What’s even weirder about this variant of Omicron, and all of its derived sub-variants, is that an infection with Omicron boosts our immunity against coronavirus infection, but not against Omicron. You are less likely to contract Delta after infection with Omicron, but re-infection with Omicron is still relevant, especially with the succession of new subvariants that followed BA.1.

This means that Omicron can continue to take center stage in the pandemic, not only by being more transmissible, but by actively eliminating other variants.

On the other hand, it could also eliminate other potentially nasty mutant variants that never get a foothold. But it’s the ability to cause reinfections, even in those who have had a recent infection, that keeps Omicron’s infection rates high, creating the long epidemic we’ve seen persist since the day it landed on our shores.

With the arrival of Omicron, the booster dose of the vaccine suddenly became important for all of us.

Not only does it protect against waning immunity, but the booster also elicits a different type of immune response than the first paired doses. Remarkably, it not only boosts protection against severe disease to the levels seen with Delta, it also restores, at least for a short time, some protection against infection, reducing infection rates by approximately 40 % during the first two months.

Not as good as Delta’s epidemic control impact, but not bad now, we’re in the shadow of the imminent next peak of the BA.5 subvariant.

This different world of infection that we now find ourselves in is the same challenge facing the whole world. We were ahead for some time in current infection rates as the northern hemisphere entered summer, and we are currently behind France, New Zealand and Singapore. We drop to 16th in the world when we look at the latest data on new per capita death reports, behind still-summer European countries.

We also only have half the daily death rate of New Zealand.

Australia’s death rate has climbed with successive waves of Omicron, and we are yet to return to the peak rate of three deaths per million that we saw then. Other countries, in their last winter when the first wave of Omicron hit, recorded death rates of between 4 and 18 per million.

We are doing relatively well, even if it is our turn to face Omicron in winter.

We are also far from the total number of deaths per capita seen in the world, grouped with Singapore, Taiwan and New Zealand among the few countries with less than 400 deaths per million inhabitants.

Canada has more than 1,000, France and the United Kingdom more than 2,000, and the United States has recorded a total of more than 3,000 deaths among every million Americans.

It doesn’t help the news that we have now had over 10,000 Covid-19 deaths in Australia, but apply the statistics from these other countries to our population size and it reaffirms the lives we have also saved.

If we matched the death rates from Canada or Denmark, we would have already had almost 30,000 Covid-19 deaths in Australia, 45,000 with German rates or 70,000 with the UK.

Sweden’s death rate translates to almost 50,000 total deaths in a population the size of Australia, but many still see this as something of a model of success.

So what comes next?

Well, if everyone eligible for a booster came out and got it tomorrow, we could keep a lid on the BA.5 wave. If those most at risk of severe illness all got their winter dose, we would also see fewer people end up in hospital as infection rates rise.

There is no guarantee that you can prevent infection, and we are now exposed to most places we go, especially in major cities. But reducing the risk could mean the difference between having an exposure and having an infection. Or between having one infection or several.

There are currently between 600 and 900 reported active cases per 100,000 people in Victoria, and you can double or triple that figure to get an idea of ​​actual infection rates. This represents between 1 and 2% of the population.

Some will self-isolate, some won’t, and many won’t even know they’re infected.

In New South Wales, new cases reported in the past four weeks exceed 100 per thousand in metropolitan Sydney and 50 in many regional areas. It is between 5 and 10% of these populations who have reported recent infection, which probably translates to up to a quarter of the population.

Masks, reminders and general precautions will not stop Omicron, but will reduce our risk of re-infection and help us get through the winter.

Antivirals are also an important secondary prevention step for those infected and at risk of serious illness. If we can limit infections and reduce the risk of disease escalation in vulnerable people, we can undermine Omicron’s main weapon, reinfection.