Research finds highly infectious B.1.1.7 virus first detected in Kent causes more severe disease
The highly infectious B.1.1.7 coronavirus variant, which swept across the UK from Kent during the autumn and is now spreading worldwide, is between 30 and 100 per cent more lethal than previous strains, a new study has shown. The research by epidemiologists from the universities of Exeter and Bristol was published in the British Medical Journal on Wednesday. It confirms provisional evidence of the variant’s increased lethality, which Prime Minister Boris Johnson announced at a Downing Street conference in January.
The scientists found that infection with the B.1.1.7 variant led to 227 deaths in a sample of 54,906 patients, compared with 141 among the same number of patients closely matched for age and demographics, who had older variants of the virus that causes Covid-19, known as Sars-Cov-2. B.1.1.7, first detected in samples from a patient in Kent in September last year, is now responsible for 98 per cent of Covid-19 cases in the UK, said Professor Sharon Peacock of Cambridge university, who heads the Covid-19 Genomics UK (Cog-UK) consortium. It is replacing older variants in many other countries and accounts for 40 per cent of cases in the US and France.
“We focused our analysis on cases that occurred between November 2020 and January 2021, when both the old variants and the new variant were present in the UK,” said Leon Danon of Bristol university, senior author of the study. “This meant we were able to maximise the number of ‘matches’ and reduce the impact of other biases. Subsequent analyses have confirmed our results.” The researchers’ central estimate is that B.1.1.7 is 64 per cent more deadly than previous variants, with 95 per cent confidence that the increased lethality is between 32 and 104 per cent.
Professor Lawrence Young, virologist at the University of Warwick, said: “The precise mechanisms responsible for increased mortality associated with the variant remain uncertain but could be related to higher levels of virus replication [within a patient] as well as increased transmissibility.” “B.1.1.7 is fuelling the recent surge in infections across Europe with over a million new cases reported last week, an increase of 9 per cent from the previous week,” Young added.
Peacock said it was impossible to predict how long B.1.1.7 would remain the dominant variant in the UK and whether it would be supplanted by new variants such as those causing concern in South Africa and Brazil at present — or by others that may evolve in future. “I don’t think we have the numbers or the evidence yet,” she said. Transmission studies suggest that variant first detected in Kent is about 50 per cent more infectious than its predecessors.
But there is no evidence to suggest that existing vaccines are significantly less effective against B.1.1.7 — an issue that is of more concern for the variants first identified in South Africa and Brazil. Sir Patrick Vallance, the government’s chief scientific adviser, told the Commons science and technology committee on Tuesday: “I don’t think we will ever stop new variants emerging . . . At the moment their advantage is largely faster transmission but once the world is vaccinated, there may be more variants that try to get round the immune response.”