AY.4.2 delta subvariant spreading in UK (> 15,000 cases) and found in USA: Get vaccinated
Facebook Twitter LinkedIn EmailOn Oct. 22 the UK Health Security Agency update on SARS-CoV-2/COVID-19 emphasized growing data to assess the significance of the delta subvariant “AY.4.2” that is gradually being transmitted better than its delta variant parent.
My key interpretations are:
- This newly designated “Variant Under Investigation VUI-21-Oct-01” is proof-of-concept that SARS-CoV-2 is still evolving and delta is not the last, or most contagious, version of SARS-CoV-2;
- The USA should expect this AY.4.2 virus will eventually also transmit in the USA, like the (faster) alpha and delta variants did in the UK before the USA;
- So far, AY.4.2 (VUI-21OCT-01) has not been reported to evade immunity, either from vaccines or by monoclonal antibodies. Thus, this is another reason to get fully vaccinated ASAP and to anticipate more transmission in populations declining vaccination or not having access to vaccines.
Crucial information from this UK report is cited below:
Summary (p. 3 of 31)
“1. 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.
2. 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.
3. AY.4.2. appears to have a modestly increased growth rate compared to Delta. ... It is still uncertain whether AY.4.2 is growing due to a biological difference.
4. The secondary attack rate for household contacts of cases with VUI-21OCT-01 was 12.4% (95% CI: 11.9% to 13.0%), higher than that observed for other Delta cases where it was 11.1% (95% CI: 11.0% to 11.2%). In non-household settings, the secondary attack rate was higher for VUI-21OCT-01 than other Delta cases, but this difference was not significant. …
5. Based on these considerations and the high level of uncertainty, AY.4.2 was designated a new Variant Under Investigation, VUI-21OCT-01.”
Surveillance case definitions (p. 10 of 31)
“AY.4.2 includes the spike mutations A222V and Y145H, as well as the mutations seen in Delta and the AY.4 lineage. … Based on this analysis, the optimal surveillance case definition is a genome meeting the existing Delta genome case definition plus any 2 of the 3 mutations (orf1ab: A2529V; S: Y145H; S: A222V) where none of the positions are wild-type. This definition is highly specific (>99.9%) and sensitive (91.6%) for the clade in question.”
Epidemiology (p. 13 of 31, with bold type added for emphasis)
“As of 21 October 2021, there are 22,017 VOC-21OCT-01 genomes in the UK dataset, linked to 15,120 cases in England. VUI-21OCT-01 accounts for 3.8%, 5.2%, and 5.9% of Delta cases in England in the weeks beginning 19 September, 26 September, and 3 October 2021 respectively.”
“Cases have been detected across all regions in England. Of the 15,120, 420 had a recent travel history, with the most frequent country of travel being or Spain (96) or Greece (75). At least 32 countries of travel have been reported.”
Severity outcomes
“These initial crude analyses do not show strong evidence of a difference in risk of hospitalisation or death between VUI-21OCT-01 and Delta. However, these analyses do not adjust for crucial factors that can influence outcomes such as age and vaccination status and should be interpreted with caution.”
