“Early growth rates for XE were not significantly different from BA.2, but using the most recent data up to 16 March 2022, XE has a growth rate 9.8% above that of BA.2.”
The latest UKHSA Technical Briefing 39, published on the 25th March 2022, states that “XE is a BA.1/BA.2 recombinant, with the majority of the genome including the S gene belonging to BA.2. XE shows evidence of community transmission within England, although it is currently <1% of total sequenced cases.
Early growth rates for XE were not significantly different from BA.2, but using the most recent data up to 16 March 2022, XE has a growth rate 9.8% above that of BA.2. As this estimate has not remained consistent as new data have been added, it cannot yet be interpreted as an estimate of growth advantage for the recombinant. Numbers were too small for the XE recombinant to be analysed by region.”
XE is a combination of BA.1 and BA.2 and is spreading about 10% faster than BA.2 in the UK, with 637 cases identified as of 22 March 2022.
There is quite a lot more information on the recombinants XD, XE and XF in the UKHSA report. You can read it below, or download it from here
UPDATE 1 – 1st March 2022 – The World Health Organisation confirms the enhanced transmissibility of XE
In their latest weekly epidemiological update, the WHO have reaffirmed UKHSA’s figures for the transmissibility for the XE recombinant
“The same process of risk assessment is applied to recombinant variants as for any other emerging variant. Since the epidemiological update published on 22 March 2022, no new evidence indicates that the recombinant variant assigned XD Pango lineage (Delta-Omicron) is associated with higher transmissibility or more severe outcomes. The XE recombinant (BA.1-BA.2), was first detected in the United Kingdom on 19 January and >600 sequences have been reported and confirmed since. Early-day estimates indicate a community growth rate advantage of ~10% as compared to BA.2, however this finding requires further confirmation. XE belongs to the Omicron variant until significant differences in transmission and disease characteristics, including severity, may be reported. WHO continues to closely monitor and assess the public health risk associated with recombinant variants, alongside other SARS-CoV-2 variants, and will provide updates as further evidence becomes available.”