Summary of SARS-CoV-2 variants of concern for increased
infectivity/transmissibility and antigenic changes (no. 27)
Updated April 21, 2023, at 9:00 am
National Institute of Infectious Diseases, Japan*This is a provisional translation of the summary of the report entitled "kansendenpasei no zoukaya kougenseino henkaga kenensareru SARS-CoV-2 nohenikabunituite (dai27hou)(https://www.niid.go.jp/niid/ja/2019-ncov/2551cepr/11879-sars-cov-2-27.html)". In the case of any dispute over translation,Japanese text prevails.

Overview of SARS-CoV-2 variantsThe Omicron variant, along with its B.1.1.529 lineage and descendant sublineages, remains dominant globally among SARS-CoV-2 variants, and there
have been no significant changes in epidemiological trends since the No. 26
report. Several sub-variants and recombinant omicron variants have beenreported. The WHO has classified XBB.1.5 as a currently circulating variant ofinterest (VOI) and BA.2.75, CH.1.1, BQ.1, XBB, XBB.1.16, XBB.1.9.1, and XBF as
currently circulating variants under monitoring (VUMs) since April 12, 2023.
However, there were no significant changes in viral characteristics, such as
severity and infectivity/transmissibility, apart from an increase in the number of
infected cases and the possibility of immune escape between subvariants. Thus,
NIID continues to classify the subvariants as before. It is important to continue
monitoring and collecting information on subvariant outbreaks through genomic
analysis in the country and quarantine.
According to the WHO weekly epidemiological updates on COVID-19 (April 13,

2022), 47.9% of XBB.1.5 sequences, 7.6% of XBB.1.9.1 and 17.6% of the other
XBB variant (excluding XBB.1.5, XBB.1.16, and XBB.1.9.1) were reported in the
12th week of 2023 (March 20-26, 2023).
In Japan, BA.5 replaced BA.2 around July 2022, and the relative sequence
prevalence among circulating variants has been dominated by BA.5, followed byan increasing proportion of BQ.1 (a sub-lineage of the BA.5.3 lineage) andBA.2.75 (a sub-lineage of the BA.2 lineage) since October 2022. The proportionof XBB variants has increased since January 2023.
Some subvariants, such as BQ.1 and XBB, exhibit characteristic mutations in thespike protein that allow the virus to evade neutralizing antibodies generated
through vaccination or previous infection and may have a growth advantage.
Some subvariants, such as XBB.1.5 in North America, XBB.1.9 in Europe, andXBB.1.16 in India, may have a growth advantage over existing sub-lineages incertain regions. However, there is no evidence that these variants spread more
rapidly than other variants.
Omicron sub-variants have emerged with specific characteristics that primarily
contribute to immune escape. There were no significant differences comparedwith the other variants, except for this feature. Global immunity and several
public health interventions in each country have resulted in less of an impact ofthe variant-specific nature on epidemic dynamics. Regular monitoring of variant
prevalence and changes in variant-specific features, including pathogenicity,virulence, transmissibility, vaccine and antiviral resistance, and clinicalpresentation, is crucial for determining appropriate interventions and rapid risk
assessment for each variant.