Waning immunity, a rise in indoor mixing and a new Omicron subvariant could bring a wave of infections this winter
An increase in Covid cases over the summer, driven by new Omicron variants, has led scientists to warn that the world is vulnerable to a new wave of infections.
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In many countries, including the UK, it can feel as if we are firmly in a “post-Covid” world. But hospitalisation rates in England, while low, are rising. Experts are blaming a mixture of “waning immunity”, a rise in indoor mixing and the appearance of a new Omicron subvariant, according to The BMJ (British Medical Journal). Across the US too, hospitalisation rates are at a historic low – but have been creeping up in the last six weeks, reported ABC News.
Is Covid now a ‘winter bug’?
As the worst of the pandemic recedes into the distance it may be tempting to think of Covid-19 as a winter illness. But experts say it would be wrong to assume the coronavirus will follow the pattern of other respiratory infections.
It may be that, as it did last year, Covid cases could peak in late December. But there is also the possibility that we experience several smaller peaks going into the winter, reported the Financial Times (FT). Although transmission increases as people mix indoors during the colder months, the same is also true in very hot weather; here, more people will be mixing indoors to escape the heat.
How concerned should we be about new variants?
Omicron subvariants are still circulating around the world and a new subvariant, BA.2.86, may be able to cause infection in people who have previously had Covid or been vaccinated against it, the US Centers for Disease Control and Prevention (CDC) has warned.
The chance of a particularly concerning new variant emerging is “too high to turn your back on”, said Eric Topol, director of the Scripps Research Translational Institute in San Diego, speaking to the FT.
According to experts Topol surveyed before the emergence of BA.2.86, the chances of an “Omicron-like event” – which put considerable pressure on the NHS as well as causing widespread workplace disruption – occurring before 2025 is somewhere between 10 and 20%.
And “all bets are off”, said Angela Rasmussen, a virologist at the University of Saskatchewan, if a variant emerges that is more transmissible than Omicron, which has been the dominant strain for the last two years.
“You would start to see [increased cases] wherever there was a nice susceptible population and not necessarily just in winter when conditions are very good for transmission,” she said. “We haven’t seen the end of this virus. It’s going to [continue to] acquire mutations and that has unpredictable results.”
So how concerned should we be about BA.2.86?
The short answer is that it is too soon to know. The CDC has said that, based on available evidence, it doesn’t know if it will pose any more of a risk than other Omicron subvariants that are currently in circulation.
But the strain appears to have a large number of genetic mutations, which mean it could circumvent any immune defences built up in the population by vaccinations and previous infections. The strain has not yet been classified as a “variant of concern” by the World Health Organization (WHO), but is a “variant under monitoring”.
However, the UK Health Security Agency (UKHSA) has brought forward its autumn vaccination plans in England. Under the revised plan, people in care homes for older people, the clinically vulnerable, those aged 65 and over, and health and social care staff can have a Covid vaccine from 11 September, rather than as initially planned in early October.
Should we be wearing masks again?
That’s what some experts are advising. Dr Trisha Greenhalgh, a University of Oxford healthcare expert and a member of the Independent Scientific Advisory Group for Emergencies, wrote on social media that in “high-risk situations I personally would wear one”, The Independent reported. “I’m currently AVOIDING such situations eg not going to cinema,” she said.
But the question of whether to mask again is a complicated one. As Simon Clarke, associate professor in cellular microbiology for the University of Reading, wrote on The Conversation in late August, masking was introduced in the UK in 2020 as part of a wide package of measures. “It seems unlikely that masking on its own, without other measures, would have much effect, if any,” he said.
