Australia is currently experiencing the longest pause between infection peaks since Omicron arrived in late 2021 and community-wide transmission took off.
As winter approaches, it’s worth taking stock of where we stand with COVID and what to expect during the colder months — especially in the Southern states and territories. The climate and the way our behavior changes at this time of year increase the transmission potential of all respiratory infectious diseases.
This will be our second winter with Omicron sub-variants, but there are signs it won’t be as challenging as the last.
Read more: Haven’t had COVID or a vaccine dose in the past six months? Consider taking a booster
Peaks and valleys
Last time we had national hospital numbers above 2,400 was on January 20, about 12 weeks ago. Us dips in the Omicron era were previously short-lived. Variant BA.1 quickly replaced BA.2 this time last year and the number of hospitals rose to over 2,400 within five weeks of the first wave. In November 2022, the number of hospitals again climbed above 2,400 with a change in subvariants after only ten weeks of delay.
Will the current break last? Most states are seeing increases in hospital numbers, but those that started climbing the earliest (New South Wales, Victoria and Tasmania) may already be seeing hospital numbers equalize. So there is hope that the current increase will not lead to such high rates of serious illness.
And we know that the recorded COVID counts for hospitals are not all admissions for COVID. Most are incidental infections. Tasmanian data show that, on average, less than a third of COVID-positive patients were admitted for COVID disease.
With each surge, a smaller proportion of COVID-positive patients are reported in ICU. The share of people on ventilators due to COVID has that too reduced to less than 10% from 30% in the first Omicron peak in January 2022. The deaths associated with each peak have also dropped with each main surge, with the summer wave just over and about half of daily deaths at its peak highlight was reported compared to our last summer. Antivirals have played an important role, but now also the immunity of the population estimated at 99.6%.
Fortunately, Omicron is less likely to cause serious illness, especially in a population with a significant degree of immunity to both vaccine and previous infection. Antivirals also reduce the risk of infections ending up in the hospital. But in times of peak infections, even a smaller proportion translates to significant loss of life among those who are vulnerable.
The shift in the dominant Omicron subvariants and their immune escape characteristics allows people to acquire new infections more quickly than if they had been exposed to the same variant they were previously infected with. Add to that the fact that we now have a mix of variants in the population, reinfections are more common and the overall infection rate will increase. So while a high level of population immunity reduces the impact of infection, multiple variants may be circulating, meaning the infection rate could still rise.
Surveillance data from NSW shows this time last year there were only two Omicron variants in circulation, BA.1. and BA.2. Now genomic testing is taking hold 12 different Omicron variants and the dominant variants continue to shift, with XBB emerging as the most dominant strain alongside XBB1.5.
Getting COVID again…and again
Re-infestation is difficult to measure and will be severely underestimated due to low reporting rates and mild or asymptomatic infections.
Reinfections help increase infection rates and therefore increase the risk of exposure to people who are at risk of serious illness if infected.
We’re still not sure if having repeated infections could change the likelihood of developing long-term COVID. It seems less likely for Omicron, especially in people affected by it mild or no symptoms.
Young adults still make up the group where most infections And reinfections prevent. They should be aware of the added risks in the winter months with more indoor mixing and ensure they have had at least one booster to keep their long COVID risk.
Read more: Long-term COVID puts some people at higher risk for heart disease – they need better long-term monitoring
Who else needs a boost?
Vaccination can still help reduce the risk of transmitting the virus, even if you become infected in the first two months after a dose. a recent US prison study found that the risk of further transmission was reduced by almost a quarter, and by 40% in those who were both vaccinated and had a recent infection, but this protection is decreasing at about 6% per week.
How this applies to a wider community is difficult to assess. People who live very close by have higher transmission rates than the general population – so it’s not clear how much reduction we would see in the community environment, even among younger adults with more workplaces and social mixing.
Younger adults, like everyone else, are not eligible for a booster until six months after their previous dose or their last infection – and many may not go six months without an infection because they are the ones in all probability to become infected during any Omicron peak less than six months apart.
The best protection against further transmission in the prison study came from a combination of vaccine and recent previous infection. Once young adults have had their first booster, continued immunity boosting from subsequent exposures or infections means they – and therefore the population – have less to gain from multiple boosters.
For those who are vulnerable to serious infections, have a weakened immune response or have shielded themselves from the community, a booster dose of the latest vaccines is still strongly recommended.
Read more: We got some key things wrong about long COVID. Here are 5 things we learned
Protecting ourselves this winter
The tools we used to manage transmission risk with previous variants don’t work now. We saw at Delta that even strict lockdown and mask mandates barely managed to control transmission with high vaccination rates.
Omicron has a number of fundamental differences that undermine these measures, including a higher number of cases a very high viral load, which means there is more virus in the aerosols people exhale. This undermines the effectiveness of maskssocial distancing and other measures.
Omicron also has one shorter incubation periodmeaning more secondary cases will be contagious before the index case knows they are infected themselves.
The Australian winter is likely to see another rise in cases. The cycle of subvariants will expose us and hasten the decline of immunity. And we will spend more time indoors together.
Being up-to-date with the latest CVOID and flu vaccines is critical for those more vulnerable to waning immunity and serious illness, and can reduce symptoms in adults who have not had a first booster or an infection in recent months.
It would be nice if all people with complaints could stay home. We would have less respiratory disease everywhere. But even then, exposure to COVID in the community would be unavoidable with so many contagious people without symptoms.
Personal protection with well-fitting masks is still possible reduce the risk that exposure to Omicron variants will lead to infection in high-risk environments. But the safest plan is still to stay home if you’re not feeling well, look for well-ventilated areas when you’re away, open windows to ventilate your home before and during visits, and be mindful of those who wear masks, as they are more than likely vulnerable and fearful.
Read more: Millions of Australians still haven’t had their COVID boosters. What message could convince them now?