Complacency concerns as BA.2 spreads: ‘We need to be wary’

Anastasia Tsirtsakis

16/03/2022 4:23:03 PM

COVID-19 infection rates are trending upwards in most Australian states and territories, with winter right around the corner.

COVID-19 Omicron subvariant BA.2.
The BA.2 subvariant of Omicron is estimated to account for more than 50% of new COVID-19 infections in some Australian states.

BA.2, a subvariant of the Omicron strain, was first detected in Australia in January.
Early reports from Denmark, where the subvariant quickly surpassed the already highly transmissible BA.1, signalled a warning for the rest of the world. Less than two months later BA.2 is the dominant variant in at least 18 countries and is already estimated to account for up to 25% of COVID cases in Australia.
The rapid spread is due to the sub-variant’s increased transmissibility, with BA.2 estimated to be up to seven times more transmissible than the original strain and up to three times more transmissible than BA.1. 
It means that after weathering an Omicron storm at the beginning of the year, cases in New South Wales are once again increasing, with over 20,000 new infections recorded on Wednesday 16 March (30,402 were announced due to a data glitch, with 10,000 of the cases positive rapid antigen tests that were registered between Sunday and Monday).

Other regions also appear to be following a similar trajectory – Victoria most recently recorded 9426 cases, while Queensland (6136) Tasmania (1859) and the Northern Territory (251) are also trending upwards.
Meanwhile, Western Australia is also experiencing a significant wave, with BA.2 currently thought to be responsible for about one quarter of new cases.
Based on what is known about the subvariant so far, Foundation Chair of Biostatistics at the University of South Australia and former World Health Organization (WHO) epidemiologist, Professor Adrian Esterman says the increase in cases ‘isn’t surprising at all’.
‘I don’t think there’s any doubt that BA.2 will increase case numbers,’ Professor Esterman told newsGP.
‘It’s much more transmissible than BA.1. In fact, its transmissibility is getting up to the level of measles, which is the most contagious disease we know.
‘So I don’t think this is a one off; I think we’ll [continue to] see increasing case numbers.’
Professor Esterman is one of a number of experts making similar predictions, among them Victoria’s COVID-19 Commander Jeroen Weimer, who forecasts case numbers will ‘continue to trend upwards over March and April’ as people spend more time gathering indoors.
While a rise in home-testing and lack of extensive genomic sequencing makes it hard to predict the prevalence of BA.2 in Australia, wastewater sequencing in Victoria shows at least half of all current cases are the subvariant.
Similar predictions are being made in New South Wales by Associate Professor James Wood from UNSW’s School of Population Health. The infectious disease modeller estimates BA.2 may already make up more than 50% of the state’s cases, with predictions they could increase to 90% by the end of March.
The jump in case numbers – which Professor Esterman says appears to be signalling a new wave – has raised particular concerns as most states and territories have significantly eased public health measures.
The risks are further heightened by complacency around booster uptake, with more than 30% of eligible Australians yet to receive a third dose and reports of GPs having to throw out thousands of doses due to lack of demand.
Professor Esterman says the prevailing attitude of most state and territory governments appears to be signalling to the public that they can return to life as normal.
While he says this is true ‘to a certain extent’, he believes we are just at the beginning of the end of the pandemic thanks to available vaccines and treatments.
‘But trouble is, we’re not at the end,’ Professor Esterman said.
‘And tomorrow there might be a new variant that comes along, which is twice as lethal as Omicron.
‘So we have to be wary that another new variant might hit us, and we have to be willing to slap on public health measures absolutely quickly, if needed.’
In the interim, the epidemiologist believes more consideration needs to be given to fourth doses for those who are most vulnerable of developing severe disease.
‘We also have to be very wary of the fact that opening up with such high case numbers puts the elderly and those with underlying health conditioners at high risk because they would have very little protection against infection now,’ Professor Esterman said.
‘I think we really do need to get the vulnerable people a fourth dose as soon as possible, and ATAGI is currently discussing that.’
Monitoring of BA.2 has revealed that the subvariant’s genetic sequence differs from BA.1, including some amino acids in the spike protein. It also appears to have a growth advantage over BA.1, according to the WHO, which lends itself to being more transmissible.
A pre-print study conducted in Japan also suggests BA.2 may potentially result in more severe disease. Researchers who infected hamsters with BA.1 and BA.2 found the subvariant was more pathogenic, with those infected with the subvariant developing more lung damage and loss of body weight.
However, real-world data from Denmark, the United Kingdom and South Africa indicate no difference in severity.
Professor Esterman says it is possible this is due to people already having immunity through widespread vaccination.
‘What we’re seeing overall is that BA.2 is actually similar in terms of its severity as BA.1; we’re seeing very similar rates of hospitalisation, pretty similar rates of ICU admission and very similar death rates,’ he said.
But that may not always be the case.
With greater transmissibility, Professor Esterman expects to see an increase in people being hospitalised.
‘It’s just a numbers game,’ he said.
‘But, of course, the other thing that’s happening is we’re getting younger and younger people who are being infected; now the majority of infected people are school kids and people in their teens and early 20s, and that’s reducing the hospitalisation rate.
‘So we won’t see hospitalisations go up dramatically, but I think they’ll either stabilise or go up a little bit, which is not so bad because at the moment states and territories can actually manage it.’
Concern still remains over long COVID, however, with general practice expected to bear the brunt.
Professor Esterman says managing this risk relies on governments taking a sensible approach, and considering the reintroduction of certain preventive measures when required. But he fears the politisation of COVID-19 may stand in the way.
‘A huge chunk of the population is sick to the teeth of COVID-19 – I known I am,’ he said.
‘And we’re looking at governments that govern by focus groups. Last year, for example, every state and territory had a daily press conference at which the Chief Public Health Officer attended; how often do we see that now?
‘And the reason, most likely, is that the governments are now no longer listening to public health advice.
‘That’s why we have to be wary, and sensible state and territory governments will [need to] have all those measures in place and [ready] at a moment’s notice to put them back in place again.’
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BA.2 COVID-19 Omicron subvariant

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