Since Australia’s first Omicron wave after borders opened late final yr, the pandemic has largely light from the information and public notion. Gone are the day by day briefings with updates on the numbers of instances, hospitalisations and deaths.
However this notion doesn’t match actuality. Whereas hospitalisation and loss of life charges have been comparatively decrease than earlier waves – because of the vaccination rollout and naturally acquired immunity – 95% of all Australia’s COVID instances have occurred because the New 12 months. The day by day fee of infections continues within the tens of hundreds.
Virtually 3,000 Australians died of COVID within the first quarter of 2022, inserting it between coronary coronary heart illness and stroke as a significant reason behind loss of life.
This yr we’ve seen each the Omicron wave and the re-emergence of influenza. After virtually disappearing for 2 years of the pandemic, the lifting of most restrictions (resembling social distancing and dealing from residence), the decline in masks use and opening of worldwide borders has allowed influenza to re-emerge.
So, how do COVID and seasonal influenza evaluate?
How lethal are COVID and influenza?
The case fatality fee – the proportion of COVID instances who die – has improved dramatically over the pandemic. Within the 2020 Victorian June-October wave, round 3% of instances died.
Within the 2021 Delta waves in New South Wales and Victoria, the loss of life fee was below 1%.
For the Omicron wave this yr – by which period a lot of the inhabitants had been vaccinated – the case fatality fee has approached 0.1%. That is corresponding to the seasonal influenza case fatality fee seen in “regular” flu years.
This drop in COVID case fatality fee has a number of causes: our excessive vaccination uptake, immunity from earlier an infection, higher therapies, and Omicron being much less lethal. The relative contributions are arduous to tease out, however vaccination is more likely to have performed probably the most vital position.
The significance of COVID vaccination was underscored by a current report estimating that internationally, vaccines have prevented between 14.4 and 19.8 million deaths. The influence would have been a lot larger with extra equitable world distribution of vaccines.
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Which is worse for unvaccinated individuals?
As of January, Omicron brought about round one-third the charges of hospitalisation and loss of life because the Delta variant. And for well-vaccinated individuals, this was corresponding to influenza.
For unvaccinated individuals, Omicron was nonetheless worse than influenza.
However any comparability of COVID variants and influenza is difficult by new sub-variants, waning immunity, and the results of vaccine booster doses.
How properly do vaccines shield in opposition to COVID variants?
Though Omicron is much less deadly than Delta, vaccination can also be much less efficient, particularly and not using a third or fourth dose.
The desk under is compiled from weekly stories from the UK of vaccine effectiveness, principally amongst these over 50 years of age. It reveals vaccine effectiveness in stopping instances has declined with the Omicron variant.
However the effectiveness in stopping hospitalisations and deaths has remained excessive, significantly with boosters.
It’s vital to interpret the apparently decrease protecting impact of vaccination in opposition to hospitalisation and loss of life through the Omicron wave with warning. Some sufferers in hospital had been discovered by the way to have a constructive take a look at for COVID, which didn’t contribute to their subsequent loss of life. Vaccination couldn’t have prevented that.
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Which is extra transmissible – COVID or the flu?
COVID has been much more infectious and spreads extra quickly than influenza.
The primary Omicron variant was estimated to be 100% extra transmissible than the unique SARS-CoV-2 virus, and 37% extra transmissible than Delta. Successive Omicron sub-variants have ever greater infectiousness – all far past that of influenza.
Seasonal influenza has a replica variety of about 1.3 , in contrast with 4.2 for Omicron. Which means one particular person with the flu spreads it to 1.3 different individuals, on common, whereas one particular person with Omicron passes it to 4.2 others. That sounds modest however these multiply, so three cycles of flu is 1.3 x 1.3 x 1.3 = 2.2 instances, whereas three cycles of Omicron is 4.2 x 4.2 x 4.2 = 74.
In consequence, we now have had practically 100-fold extra COVID than influenza instances this yr, and COVID will doubtless stay the key reason behind hospitalisations and deaths over winter.
One illustration of that is information from america: in January 2022, extra US kids died of COVID in a single month than in any of the ten earlier years from influenza.
What are we more likely to see in future?
In contrast with many international locations, Australia has completed properly in controlling COVID. It has minimised each the influence of sickness and the financial burden, via worldwide and state border closures, intermittent lockdowns in some states, and a really profitable preliminary vaccine rollout.
However the COVID pandemic just isn’t over, and we are going to expertise additional waves of an infection with new sub-variants resembling Omicron BA.4/5 (now 35% of instances in NSW), which is able to proceed to trigger sickness, hospitalisation and loss of life.
Sadly, Australia’s booster uptake has been a lot slower than the preliminary vaccination marketing campaign and has virtually stalled. This complacency is harmful.
Up to now three years we now have skilled the pandemic and a collection of pure disasters in Australia. Fatigue and a need to maneuver previous COVID is totally comprehensible however carries substantial threat.
Throughout winter, we should redouble our efforts to take care of inhabitants immunity via vaccine boosters mixed with affordable protecting measures. Make sure that your COVID and influenza vaccines are up-to-date, keep away from crowded locations (or put on a masks when you can’t), and keep away from others if in case you have any respiratory signs.
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Paul Glasziou receives funding from NHMRC for analysis into antimicrobial resistance, non-drug therapies, and low-value care.
David Henry is an investigator within the Centre of Analysis Excellence in Medicines Intelligence, funded by the NHMRC