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Yesterday we saw the UK Health Security Agency (UKHSA) elevate the AY.4.2 variant from being simply monitored to a VUI (Variant Under Investigation). Several hours later, the same agency released a Technical Briefing (#26) dedicated primarily to this emerging COVID variant.
While it is far from clear whether AY.4.2 will become the next COVID threat, it does appear to be making inroads against the dominant Delta B.1.617.2 parental strain in the UK, and their early analysis suggests it may have a transmission advantage.
That said, UK researchers are quick to add this is very preliminary information and it carried a high degree of uncertainty. So far, we've not seen AY.4.2 making the same strides against Delta here in the United States.
I've only included a few excerpts from a much longer, and highly detailed, 31-page PDF report. Follow the link to download and read it in its entirety.
22 October 2021
Summary This extra report has been produced to provide information on the new Variant Under Investigation VUI-21OCT-01, AY.4.2. The specialist technical briefings contain early data and analysis on emerging variants and findings have a high level of uncertainty.
In summary:
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. Growth rates are included here and similar findings were reported by another Variant Technical Group contributor using a different method. 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.
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. No significant variation between regions was observed.
5. Based on these considerations and the high level of uncertainty, AY.4.2 was designated a new Variant Under Investigation, VUI-21OCT-01.
6. 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 hospitalisations 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 4All risk assessments are published separately, except for Gamma, which was published within Technical Briefing 7 and Alpha within Technical Briefing 9. As Delta is the dominant variant in the UK, epidemiological data in the weekly surveillance report is also relevant.
(SNIP)
2.2 Epidemiology of VUI-21OCT-21 in England
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 (Figure 4). Data are incomplete for more recent weeks.
Variant prevalence for all cases in England as of 21 October 2021 is shown in Figure 4, by region in Figure 5 and travel status in Figure 6. Figure 7 shows AY.4.2 as a proportion of all Delta cases in England using Pangolin lineage call.
Cases have been detected across all regions in England (Table 5 and Figure 8). 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. Age data are shown in Figure 9.
Severity outcomes
To assess severe outcomes from VUI-21OCT-01 outcomes of cases between 15 May 2021 and 23 September 2021 were assessed and compared against Delta cases from the same time period. This time period was selected to cover the emergence of VUI-21OCT-01 and allow 28 days since first specimen to elapse to assess outcomes.
Information on attendance to emergency care is derived from the Emergency Care Data Set (ECDS) and Secondary Uses Service (SUS), provided by NHS Digital. These data only show whether a case has attended emergency care at an NHS hospital and was subsequently admitted as an inpatient. The data does not include cases who were directly admitted without first presenting to emergency care.
ECDS and SUS reporting is lagged, where NHS trusts routinely provide monthly data by the 21st of the following month. However, some trusts report daily data, and the linkage between coronavirus (COVID-19) cases and ECDS data is updated twice-weekly.
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.
