#17,240
Although we don't have enough data to say with any certainty - one way or another - about its relative severity, everything we've seen suggests that Omicron XBB.1.5 may be the most immune evasive, and transmissible, variant to date.
Last week the ECDC published:
Risk assessment
13 Jan 2023
According to the current ECDC assessment, there is moderate probability of XBB.1.5 becoming dominant in the EU/EEA and causing a substantial increase in the number of COVID-19 cases within the next one to two months.
And the WHO published:
WHO Rapid Risk Assessment On Omicron XBB.1.5
And earlier this month we looked at a preprint (see Enhanced Transmissibility of XBB.1.5 is Contributed by Both Strong ACE2 Binding and Antibody Evasion), which that found that XBB.1.5 not only had enhanced antibody evasion compared to XBB and BQ.1, it also appears to have a substantially increased hACE2-binding affinity as well.
All of which suggests that prior infection and/or vaccination will provide only limited protection against reinfection with this strain, although it should still help reduce the severity of any breakthrough infection.
Overnight the Sato Lab in Japan released their own (preprint) analysis of XBB.1.5, which confirms much of what has been stated previously about its immune escape and transmissibility. I've only posted the abstract, but you can read the full report at the link below.
I'll have a brief postscript when you return.
Enhanced transmissibility, infectivity and immune resistance of the SARS-CoV-2 Omicron XBB.1.5 variant
Keita Uriu, Jumpei Ito, Jiri Zahradnik, Shigeru Fujita, Yusuke Kosugi, Gideon Schreiber, The Genotype to Phenotype Japan (G2P-Japan) Consortium, Kei Sato
doi: https://doi.org/10.1101/2023.01.16.524178
Preview PDF
Abstract
In 2022, we have elucidated the characteristics of a variety of newly emerging SARS-CoV-2 Omicron subvariants. At the end of 2022, the XBB.1.5 variant, an descendant of XBB.1 that acquired the S:F486P substitution, emerged and is rapidly spreading in the USA and is the latest variant of concern. Although the features of XBB.1.5 was already reported by another group as a preprint, we think multiple and independent evaluations important, and these reports are crucial for sustained global health.In this study, our epidemic dynamics analysis revealed that the relative effective reproduction number (Re) of XBB.1.5 is more than 1.2-fold greater than that of the parental XBB.1, and XBB.1.5 is outcompeting BQ.1.1, the predominant lineage in the USA as of December 2022. Our data suggest that XBB.1.5 will rapidly spread worldwide in the near future.Yeast surface display assay and pseudovirus assay respectively showed that the ACE2 binding affinity and infectivity of XBB.1.5 is 4.3-fold and 3.3-fold higher than those of XBB.1, respectively. Moreover, neutralization assay revealed that XBB.1.5 is robustly resistant to BA.2 breakthrough infection sera (41-fold versus B.1.1, 20-fold versus BA.2) and BA.5 breakthrough infection sera (32-fold versus B.1.1, 9.5-fold versus BA.5), respectively.Because the immune resistance of XBB.1.5 is comparable to that of XBB.1, our results suggest that XBB.1.5 is the most successful XBB lineage as of January 2023 by acquiring the S:F486P substitution to augment ACE2 binding affinity without losing remarkable immune resistance, which leads to greater transmissibility.
Given what we know about `Long COVID', and the increased risks following reinfection (see Nature: Acute and Postacute Sequelae Associated with SARS-CoV-2 Reinfection), and the loss of the last of our `game-changing' monoclonal antibody treatments (see FDA Withdraws EUA (Emergency Use Authorization) For Last COVID Monoclonal Antibody: Bebtelovimab), the emergence of a more transmissible Omicron variant as we go into our 4th year of this pandemic is far from ideal.
The good news is, vaccines (and boosters) can still provide some protection, and masks and hand sanitizers can still help reduce your risk of infection.
Assuming, of course, you are willing to commit to using them.
