New Virus Variant Quickly Gains in the UK

The United Kingdom (UK) Health Security Agency Technical Briefing #28, published on November 12, 2021, continues to disclose the detailed COVID-19 surveillance analyses which contribute to the variant risk assessments and designation of new variants of concern (VOC) and variants under investigation (VUI).

In summary:

• There are four current VOCs and 9 VUI. There have been no new VOCs or VUIs in the UK classification since the last briefing.
• Delta remains the predominant variant accounting for approximately 99.8% of sequenced cases in England from October 10 to November 8, 2021.
• The Delta sublineage AY.4.2 (VUI-21OCT-01) accounts for 13% of Delta cases from October 24, 2021, to October 30, 2021, and 14.7% in the week of October 31, 2021, to November 6, 2021.
• Vaccine effectiveness analysis does not suggest a significant reduction in vaccine effectiveness for AY.4.2 compared to other Delta viruses. In addition, analysis using the standard test-negative case-control study does not indicate a decrease in vaccine effectiveness for AY.4.2 compared to non-AY. 4.2.
• Preliminary viral neutralization studies with post-vaccination sera against AY.4.2 virus shows a 2.8 fold drop compared to the wild-type virus, similar to Delta, which showed a 3.2 fold drop in neutralization (Genotype to Phenotype consortium).
• A new risk assessment for AY.4.2 has been published and is available here.

A separate report is published covering surveillance data on all other VOCs and VUIs. And, The Agency has curated a repository from March 5, 2021, containing the up-to-date genomic definitions for all VOCs and VUIs. The repository is accessible on GitHub.