Updated: April 15, 2021 9:35:54 am
Two new studies, published in Lancet Infectious Diseases and Lancet Public Health, have found no evidence that people infected with B.1.1.7 (UK variant of coronavirus) experience worse symptoms or a heightened risk of developing “long Covid” compared to those infected with a different Covid-19 strain. However, viral load and R-number were higher for B.1.1.7, adding to growing evidence that it is more transmissible than the first strain detected in Wuhan, China, in December 2019.
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The emergence of new variants, including B.1.1.7, has raised concerns that they could spread more easily and be more deadly, and that vaccines developed based on the original strain might be less effective against them. Preliminary data on B.1.1.7 indicates that it is indeed more transmissible, with some evidence suggesting it could also be associated with increased hospitalisations and deaths.
Of the two new studies, the one in Lancet Infectious Diseases is a whole-genome sequencing and cohort study involving Covid-19 patients admitted to University College London Hospital and North Middlesex University Hospital between November 9 and December 20, 2020. This was a critical time point when both the original and B.1.1.7 variants were circulating in London, the vaccination programme was just starting, and before cases surged in early 2021.
The authors compared illness severity in people with and without B.1.1.7 and calculated viral load. Among 341 patients who had their Covid-19 test swabs sequenced, 198 had B.1.1.7 and 143 had a non-B.1.1.7 infection. No evidence of an association between the variant and increased disease severity was detected, with 36% (72) of B.1.1.7 patients becoming severely ill or dying, compared with 38% (53) of those with a non-B.1.1.7 strain.
Patients with the B.1.1.7 variant tended to be younger, with 55% (109) of infections in people under 60 compared with 40% (57) for those who did not have B.1.1.7. Infections with B.1.1.7 occurred more frequently in ethnic minority groups, accounting for 50% (86/172) of cases that included ethnicity data, compared with 29% (35/120) for non-B.1.1.7 strains.
Those with B.1.1.7 were no more likely to die than patients with a different strain, with 16% (31) of B.1.1.7 patients dying within 28 days compared with 17% (24) for those with a non-B.1.1.7. infection.
To gain insights into the transmissibility of B.1.1.7, the study authors used data generated by PCR testing of patient swabs to predict their viral load – the amount of virus in a person’s nose and throat. The data analysed – known as PCR Ct values and genomic read depth – indicated that B.1.1.7. samples tended to contain greater quantities of virus than non-B.1.1.7 swabs.
Dr Eleni Nastouli, from University College London Hospitals NHS Foundation Trust, said: “One of the real strengths of our study is that it ran at the same time that B.1.1.7 was emerging and spreading throughout London and the south of England. Analysing the variant before the peak of hospital admissions and any associated strains on the health service gave us a crucial window of time to gain vital insights into how B.1.1.7 differs in severity or death in hospitalised patients from the strain of the first wave.”
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