Key facts
- Since the last update on 25 April 2025, and as of 28 May 2025, NB.1.8.1 (XDV descendant) was added as a variant under monitoring (VUM).
- Note that for this update, sufficient data for estimating variant proportions during the reporting weeks is only available from two EU/EEA countries. The statistics below therefore only represent a limited part of the EU/EEA.
- The VOI and VUM median proportions in the EU/EEA for weeks 19-20, based on two reporting countries, are currently:
-KP.3 32.8% (range: 8.5%-57.1%)
-BA.2.86 19.1% (range: 7.1%-31.0%)
-XEC 7.8% (range: 7.1%-8.5%)
-LP.8.1 33.2% (range: 21.4%-45.1%)
Overview
Since the last update on 25 April 2025, and as of 28 May 2025, NB.1.8.1 was added as a variant under monitoring (VUM) and de-escalated variants.
NB.1.8.1 is a descendent of the XDV lineage, which in turn descended from BA.2.86. NB.1.8.1 features the following additional mutations relative to BA.2.86: T22N, F59S, G184S, A435S, L455S, F456L, T478I and Q493E. While T22N, F59S, L455S, F456L and Q493E have featured in other BA.2.86 descendants such as KP.3, XEC and LP.8.1, three are unique to NB.1.8.1: G184S, A435S and T478I.
VUM classification is based on evidence of an increased growth rate, relative to other circulating variants, globally, with a limited number of sequences (n=18) reported in the EU/EEA as of 25 May 2025. While this VUM classification serves to highlight the evolution of a SARS-CoV-2 variant that is outcompeting other strains, it is too early to assess if NB.1.8.1 will have any substantial epidemiological impact in the EU/EEA, with current SARS-CoV-2 circulation at very low levels. There is currently no evidence of increased severity for NB.1.8.1 and no significant impact on vaccine effectiveness against severe disease is anticipated for currently available vaccines, although further laboratory and clinical studies are awaited [1, 2, 3, 4].
The VOI median proportions in the EU/EEA for weeks 19-20, based on two reporting countries, are currently:
KP.3: 32.8% (range: 8.5%-57.1%, IQR: 20.6%-45.0%)
BA.2.86: 19.1% (range: 7.1%-31.0%, IQR: 13.1%-25.0%).
The VUM median proportions in the EU/EEA for weeks 19-20, based on two reporting countries, are currently:
XEC: 7.8% (range: 7.1%-8.5%, IQR: 7.5%-8.1%)
LP.8.1: 33.2% (range: 21.4%-45.1%, IQR: 27.3%-39.2%).
The calculations are based on data reported to GISAID, as of 25 May 2025. Note that for this update, sufficient data for estimating variant proportions during the reporting weeks is only available from two EU/EEA countries. The statistics below therefore only represent a limited part of the EU/EEA.
ECDC assessment
Low SARS-CoV-2 transmission, reduced reporting and low testing volumes in sentinel systems all have an impact on ECDC’s ability to accurately assess the epidemiological situation, including variant circulation.
The EU/EEA population overall has a significant level of hybrid immunity (prior infection plus vaccination/boosters), conferring protection against severe disease. The variants currently circulating that are classified as VOI or VUM are unlikely to be associated with any increase in infection severity compared with previously circulating variants, or a reduction in vaccine effectiveness against severe disease. However, older individuals, those with underlying conditions, and individuals who have previously not been infected could develop severe symptoms if infected. Vaccination continues to be protective, with stronger protection against more severe disease, although this protective effect wanes over time. Vaccination of individuals at high risk of severe outcomes (e.g. older adults) remains important.
Actions
In order to assess the impact of emerging SARS-CoV-2 sub-lineages and their possible correlation with increases in COVID-19 epidemiological indicators, it is important that countries sequence positive clinical specimens and report to GISAID and/or TESSy.
For the latest update on SARS-CoV-2 variant classifications, please see ECDC's webpage on variants. Variant surveillance data, including the distribution of VOC and VOI variant proportions in the EU/EEA and detailed country-specific COVID-19 updates are available as part of the European Respiratory Virus Surveillance Summary (ERVISS).
Routine updates on the SARS-CoV-2 variant classification through the Communicable Diseases Threats Report (CDTR) will be provided on a monthly basis at a minimum.