The UK Health Security Agency has created a new report providing information on the new Variant Under Investigation VUI-21OCT-01, AY.4.2 (Delta Plus). The specialist technical briefings contain early data and analysis on emerging variants and findings have a high level of uncertainty.
In summary: AY.4.2. accounts for a slowly increasing proportion of cases in the UK. It is also present in multiple other countries on GISAID and is seen in travellers to the UK from a large number of countries. It is not clear where it originated or when. This lineage has the mutations of Delta and AY.4, and in addition S: A222V and Y145H. These mutations are in the N terminal domain.
They could plausibly be biologically significant but there is minimal laboratory evidence. AY.4.2. appears to have a modestly increased growth rate compared to Delta.
A high observed growth rate may be due to a biological change in the virus (transmissibility or immune escape) or to epidemiological context, such as being introduced into an area or population subgroup with high existing levels of transmission. It is still uncertain whether AY.4.2 is growing due to a biological difference. The secondary attack rate for household contacts of cases with VUI-21OCT-01 was 12.4% higher than that observed for other Delta cases where it was 11.1%.
In non-household settings, the secondary attack rate was higher for VUI-21OCT-01 than other Delta cases, but this difference was not significant. No significant variation between regions was observed. Based on these considerations and the high level of uncertainty, AY.4.2 was designated a new Variant Under Investigation, VUI-21OCT-01. Preliminary epidemiology and some of the supporting data used in the VUI assessment are included in this report. In addition, comparative analyses of deaths, hospitalisation, and vaccine effectiveness have commenced and will be reported once available.
Crude data on deaths and hospitalizations are included in this report for information but are not definitive analyses. Further severity and transmissibility modelling will be undertaken. Pseudovirus work has been initiated and residual biological materials are being cultured for live virus. 7. Lambda (C.37) and C36.3 have been de-escalated as of the 20 October 2021 to variants in monitoring. SARS-CoV-2 variants of concern and variants under investigation 4 All risk assessments are published separately, except for Gamma.
As of October 21, 2021, there are 22,017 VOC-21OCT-01 genomes in the UK dataset, linked to 15,120 cases in England. Cases have been detected across all regions in England. They also found 1,187 sequences on GISAID meet the VUI-21OCT-01 definition from 33 countries. The case definition has not been validated on international data and will be further assessed; results are provisional. Using the surveillance case definition. sequences are identified from Denmark (291), Germany (253), United States (113), Poland (112), Italy (67), Ireland (66), Romania (61), Belgium (43), France (22), Netherlands (21), India (20), Switzerland (20), Spain (15), Norway (13), Portugal (10), Lithuania (8), Czechia (7), Czechia (7), Malaysia (7), Slovakia (7), Canada (6), Sweden (6), Austria (3), Estonia (2), Finland (2), Greece (2), Iceland (2), Singapore (2), Aruba (1), Australia (1), Bangladesh (1), Bulgaria (1), Japan (1), and Mexico (1).
