The virus is now in a race with the vaccines and the victor is increasingly uncertain
The UK’s fine performance in sequencing Sars-CoV-2 genomes allows Public Health England to publish detailed analyses on the progress of variants and the latest report represents the changing of the guard. The B.1.1.7 lineage, first identified in Kent, had been dominant in the UK, but the B.1.617.2 lineage, first identified in India, comprised 58% of the most recent sequences, up from 44% the week before. There are strong regional differences, with under 10% of cases in Yorkshire and the Humber being the Indian-identified variant, while in north-west England that share is over 60%.
The main concern is about increased risk of transmission and reports also include estimates of what is known as the “secondary attack rate” (SAR), which simply means the proportion of an infected person’s contacts who also get infected. Using NHS test-and-trace data for recent non-travel cases, the estimated SAR for the B.1.1.7 variant was 8.1% (+/- 0.2%), while for the variant identified in India it was substantially higher at 13.5% (+/- 1.0%) – although these are likely to understate the true values due to the limitations of contact tracing.
