The new variant has a transmission advantage of 0.4 to 0.7 in reproduction number compared to the previously observed strain.
The findings come in a pre-print authored by a collaborative team from Imperial College London, University of Edinburgh, Public Health England (PHE), the Wellcome Sanger Institute, the University of Birmingham and theCOVID-19 Genomics UK (COG-UK) Consortium+.
New variant of concern
"This higher transmissibility will make control more difficult and further accentuates the urgency of rolling out vaccination as quickly as possible."
Professor Neil Ferguson, Imperial College COVID-19 Response Team
All viruses undergo genetic changes which are called mutations, and through selection pressure can result in different variants. The variant of SARS-CoV-2 (the virus causing COVID-19) originally termed lineage B.1.1.7, was detected in November 2020 and is rapidly spreading across England. Several genetic changes (substitutions and deletions) have immunological significance and are associated with diagnostic test failures. The absence of S gene target in an otherwise positive PCR test appears to be a highly specific marker for the B.1.1.7 lineage, which has now been designated a Variant of Concern (VOC) 202012/01 by Public Health England.
Using a variety of statistical approaches, the team evaluated the relationship between transmission and the frequency of the new variant across regions in the UK over time.
Using whole genome prevalence of different genetic variants through time and phylodynamic modelling (dynamics of epidemiological and evolutionary processes), researchers show that this variant is growing rapidly.
The study finds a high correlation between VOC frequency and something called S-gene target failure (SGTF) in routine PCR testing of community cases. This allowed the researchers to use SGTF frequency as an estimate for VOC and non-VOC occurrence by region over time showing that VOC frequency is associated with epidemic growth in nearly all areas.
There is a consensus among all analyses that the VOC has a substantial transmission advantage (increased transmission compared to non-VOC), with the estimated difference in reproduction numbers between VOC and non-VOC ranging between 0.4 and 0.7, and the ratio of reproduction numbers varying between 1.4 and 1.8.
These higher infection levels took place despite the high levels of social distancing in England. Extrapolation to other transmission contexts requires caution, the researchers note.