Summary of SARS-CoV-2 variants of concern for increased infectivity/transmissibility andantigenic changes (no. 26)
Updated March 24, 2023, at 9:00 am
National Institute of Infectious Diseases, Japan*This is a provisional translation of the summary of the report entitled "kansen-denpasei nozoukaya kougenseino henkaga kenensareru SARS-CoV-2 no henikabunituite (dai26hou)(https://www.niid.go.jp/niid/ja/2019-ncov/2551-cepr/11879-sars-cov-2-26.html)". In the caseof any dispute over translation, Japanese text prevails.
Overview of SARS-CoV-2 variantsThe Omicron, the B.1.1.529, and its descendent lineages are still dominant globally
among SARS-CoV-2 variants, with no significant changes in epidemiological trends compared tothe No. 25 report. The World Health Organization (WHO) refers to all B.1.1.529 sub-lineages
and recombinants as Omicron, whereas NIID has classified omicron variants as variants of concern(VOCs).
The omicron variants are genetically divergent, and WHO and European Centre for Disease
Prevention and Control (ECDC) have classified them as variants under monitoring (VUM), variantsof interest (VOIs), and VOCs. The WHO has classified XBB.1.5 as currently circulating variants ofinterest (VOIs), and BQ.1, BA.2.75, CH.1.1, XBB and XBF as currently circulating variants undermonitoring (VUMs), respectively, since March 15. However, the information lacks significant changes
in viral characteristics such as severity or infectivity/transmissibility, apart from the predominanceof the increased number of infected cases and the possibility of immune escape betweensubvariants. Thus, NIID continues the current classification of the subvariants. It is important tocontinue monitoring and collecting information on sub-variant outbreaks through genomic analysis
in the country and quarantine.
They accounted for 98.4% of the sequences submitted to GISAID from February 13 toMarch 13, with few reports of other lineages (WHO, 2023). The XBB variant accounted for 44.8%of the detected subvariants and became dominant in five of the six WHO regions, except theWestern Pacific region, in the 8th week of 2023 (February 20-26).
The top three variants globally were XBB.1.5 (35.1%), BQ.1 (15.1%), and XBB, excluding
XBB.1.5 (9.7) (WHO, 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 by anincreasing proportion of BQ.1 (a sub-lineage of the BA.5.3 lineage) and BA.2.75 (a sub-lineageof the BA.2 lineage) since October 2022.

Some subvariants, such as BQ.1 and XBB, exhibit characteristic mutations in the spike
protein that allow the virus to evade neutralizing antibodies through vaccination, infection, and/or
show a growth advantage. Some subvariants, such as XBB.1.5, are increasing in North America andmay have a growth advantage over existing sub-lineages in certain regions. However, there wereno findings that they spread more rapidly than the other variants.
Omicron subvariants have emerged with specific characteristics that primarily contributeto immune escape. There were no significant differences from the other variants except for them.
Global immune status and some public health interventions in each country have resulted in lessinfluence of variant-specific nature on epidemic dynamics. It is crucial to determine appropriate
interventions based on regular monitoring of variant prevalence and changes in variant-specificfeatures, including virulence, transmissibility, vaccine and antiviral resistance, clinical presentation,and rapid risk assessment for each variant.
COVID-19 surge has been reported in China since November 2022. China decided tocease the zero-COVID-19 policy on December 7, 2022. The number of daily cases started
increasing in late December 2022, and there was a late increase in severe or hospitalized patientsin early January 2023. Recent reports have demonstrated a decreasing trend in the number ofdaily cases. According to sequences submitted to GISAID from China, BA.5.2.48 and BF.7.14 wereconsidered dominant. These subvariants are thought to have no significant effect on immune escape,transmissibility, and severity compared with BA.5.2 and BF.7, which have already been detectedin Japan.
Japan conducted screening tests for all passengers with a travel history of China(excluding Hong Kong and Macau) (within seven days) and all passengers directly from China(excluding Hong Kong and Macau) as they arrived from December 30, 2022. These test resultsrevealed that BA.5.2 and BF.7 are dominant in these passengers from China. The quarantine testing
policy has changed since March 1 to test a maximum of 20% of the samples from passengers fromChina (excluding Hong Kong and Macau).