Delta subvariant less likely to cause symptoms: UK study

LONDON • A Delta subvariant that is spreading in Britain is less likely to lead to symptomatic Covid-19 infection, according to a coronavirus prevalence survey which also found that overall cases had dropped from a peak last month.

The Imperial College London React-1 study, released yesterday, found that the Delta Plus subvariant, known as AY42, had grown to account for nearly 12 per cent of samples sequenced, but only a third had "classic" Covid-19 symptoms, compared with nearly a half of those with the currently dominant Delta lineage AY4.

Two-thirds of people with AY42 had a symptom of some sort, compared with more than three-quarters of those with AY4.

AY42 is thought to be slightly more transmissible but it has not been shown to cause more severe disease or evade vaccines more easily than the Delta variant.

The researchers said that asymptomatic people might self-isolate less, but also that people with fewer symptoms might spread it less easily through coughing and also may be unlikely to get severely ill.

"It is preferentially appearing to be more transmissible," Imperial College epidemiologist Paul Elliott told reporters. "It does seem to be less symptomatic, which is a good thing."

Imperial had previously released interim results that showed Covid-19 prevalence was at its highest on record last month, with infections highest among children.

The full results of the latest round of the study, conducted between Oct 19 and Nov 5, confirmed what daily recorded cases and other prevalence surveys have shown - that infection levels had dropped from that peak, corresponding with a half-term school holiday late last month.

The React-1 study also found that booster doses reduced the risk of infection in adults by two-thirds, compared with people who had two doses.

REUTERS