A more transmissible subtype of the Omicron Covid-19 variant is on course to become dominant within weeks, scientists said yesterday, as new data suggested that coronavirus cases were again rising.
There are about 159,500 new daily symptomatic cases of Covid across the UK, according to the Zoe Covid Study — an increase of about 10 per cent from last week.
The trend has been driven by a sharp rise in cases among people under 18, where there are now nearly 70,000 daily cases. Infections are also rising in the 35-55 age group, suggesting transmission to parents. In all other age groups cases have stopped falling.
Professor Tim Spector, who heads the Zoe project, said: “The bounce back in case numbers just as we lift restrictions has come sooner than many expected. But it’s not surprising — we’ve seen the end of school holidays repeatedly usher in a rapid rise in cases among children, which then cross over into parents and school staff.”
He noted growing evidence that a subtype of Omicron called BA.2 may be more infectious. “One in 20 new cases had [the BA.2] variant last week, and as it’s doubling every few days this should predominate within a month,” he said.
BA.2 now probably accounts for about 8 per cent of Covid cases in South East England, where levels are highest, according to estimates by Professor Alastair Grant of the University of East Anglia. For London he estimates around 7 per cent, and for the East of England about 6 per cent.
Early assessments from Denmark, where BA.2 is dominant, suggest it could spread about 50 per cent more quickly than BA.1. However, Professor Francois Balloux, director of the UCL Genetics Institute, said it was too early to be sure how much of a growth advantage it has.
In terms of the important spike protein, which the coronavirus uses to break into cells, BA.2 looks very similar to BA.1. This indicates that “infection from either sub-lineage should provide robust immunity against the other one, as well as against itself,” Balloux said.
The origins of BA1 and BA2 are shrouded in mystery. “They are very intriguing from a scientific point of view,” Balloux said.
“But from an epidemiological point of view, I’m not particularly worried — it might increase the number of people exposed during this wave, but this is likely to have a relatively marginal impact.”
Separately, new data confirmed that a booster vaccine offers high levels of protection. The risk of death for those aged 50 or over was reduced by 95 per cent, two weeks after receiving a third booster dose. For the same group, the risk had been reduced by 60 per cent six months after the second dose.