New sequencing studies shed more light on the B.1.1.7 SARS-CoV-2 variant

Written by Francesca Lake (Editor-in-Chief)

Two new studies have shed light on the B.1.1.7 variant, suggesting that while it is more transmissible, it does not increase severity.

The B.1.1.7 variant of SARS-CoV-2 was first identified in the UK in December 2020, and is now one of three well-known variants – including P.1 (first identified in Brazil) and B.1.351 (first identified in South Africa) – that have triggered a wave of efforts to examine their impact on epidemiology and the efficacy of vaccines and therapeutics.

The first study reports on disease severity and viral loads from a cohort of patients with COVID-19 admitted to two London (UK) hospitals between November 9 and December 20 2020, a time point shortly before a surge in cases, when the B.1.1.7 variant was circulating in London and the vaccination program was in its infancy.

With B.1.1.7 making up 58% of infections, there was no association found with severity, with 36 and 38% of patients with a B.1.1.7 or non-B.1.1.7 infection, respectively, becoming severely ill or dying. A regression analysis indicated that B.1.1.7 was no more likely to result in severe disease after controlling for hospital, sex, age, ethnicity and underlying health conditions.

However, PCR testing confirmed that patients with the B.1.1.7 variant had a greater viral load.

“Analyzing 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 hospitalized patients from the strain of the first wave,” noted corresponding author Eleni Nastouli (University College London, UK). “Our study is the first in the UK to utilize whole-genome sequencing data generated in real-time and embedded in an NHS clinical service and integrated granular clinical data.”

Nastouli went on to note that the approach is a good example for other studies that may need to be performed on newly emerging variants.

The second study – also observational – combined data from 26,920 UK-based users of the COVID Symptom Study app who had tested positive between 28 September 2020 and 27 December 2020 with surveillance data from the COVID-19 UK Genetics Consortium and Public Health England. Again, this study covered an apposite time period, when the B.1.1.7 variant was first growing in proportion across London and the South East of England.

“We could only do this by aggregating two large sources of data: the extensive genetic sequencing of viral strains performed in the UK, and symptom and testing logs from millions of users on the COVID-symptom Study App,” explained co-lead author Claire Steves (King’s College London, UK).

The adjusted results again confirmed that the B.1.1.7 variant increases transmission, increasing the R number 1.35 times compared with the original strain. However, the results also indicate that the variant responded to lockdown measures and did not escape immunity gained following exposure to the original virus. There appeared to be no effect on the number or type of symptoms experienced, including ‘long COVID’. It also appeared that the reinfection rate was not affected by the variant.

Again, the study protocol will also be of use for new variants: “If further new variants emerge, we will be scanning for changes in symptom reporting and reinfection rates, and sharing this information with health policymakers,” Steves noted.

Overall, these two studies are encouraging. While reporting some results contrary to others that require confirmation, they do support the consensus that the B.1.1.7 variant increases transmissibility, and suggest that current testing infrastructure will remain effective.