Avian Flu Diary: WHO TAG-VE Risk Assessment On COVID VUM (Variant Under Monitoring) NB.1.8.1

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The most recent CDC Nowcast (see above) indicates that COVID variant LP.8.1 is currently responsible for nearly 3/4ths of the COVID cases identified in the United States, but that another variant - XFC - is making some solid inroads.

Even with limited surveillance, at least 13 other variants are known to be circulating in the United States. Around the globe, COVID's diversity is even greater.

COVID continues to evolve a furious rate - both in humans and in non-human specie s - and many more COVID variants are expected to continue to come off the evolutionary assembly line going forward. While we've not seen any huge changes in its behavior since the arrival of the Omicron lineage in late 2021, there are no guarantees that can't happen again.

Far fewer people are getting COVID boosters these days, and most people have abandoned masks and other NPIs to prevent infection, believing the risks of severe illness to be low.

Still, the virus claims hundreds of American lives every week, and studies continue to find persistent and often severe sequelae linked to COVID infection (see Brain, Behavior & Immunity: COVID-19 may Enduringly Impact Cognitive Performance and Brain Haemodynamics in Undergraduate Students).

Over the past few weeks there have been numerous media reports of a surge in COVID cases in China, Hong Kong, and Taiwan much of which has been attributed to an emerging NB.1.8.1 variant (see CBS News U.S. reports cases of new COVID variant NB.1.8.1 behind surge in China).

Meanwhile, Hong Kong's most recent (May 22nd) COVID report indicates their largest surge in severe and/or fatal COVID cases in nearly a year.

Other, far less reliable reporting (often from China's dissident press) paint a more dire picture. The reality is, anything - good or bad - we hear out of China has to be taken with a very large grain of salt. But it is fair to say their is a surge in COVID cases, and deaths, in Asia right now.

Since the virus is continually evolving, and most people now eschew the booster shots, our collective immunity wanes a little bit more each day. New surges in COVID are all but inevitable going forward.

This morning we have a recently released risk assessment on NB.1.8.1 variant from the WHO's TAG-VE (Technical Advisory Group on SARS-CoV-2 Virus Evolution), which currently - and based on limited information - puts the risk from this emerging subvariant as `Low'.

I've included some excerpts from a far more detailed report, follow the link to read it in its entirety. I'll have a brief postscript after the break.

WHO TAG-VE Risk Evaluation for SARS-CoV-2 Variant Under Monitoring: NB.1.8.1
Executive Summary
NB.1.8.1 has been designated a SARS-CoV-2 variant under monitoring (VUM) with increasing proportions globally, while LP.8.1 is starting to decline. Considering the available evidence, the additional public health risk posed by NB.1.8.1 is evaluated as low at the global level. Currently approved COVID-19 vaccines are expected to remain effective to this variant against symptomatic and severe disease. Despite a concurrent increase in cases and hospitalizations in some countries where NB.1.8.1 is widespread, current data do not indicate thatthis variant leads to more severe illness than other variants in circulation.
Initial Risk Evaluation of NB.1.8.1, 23 May 2025
NB.1.8.1 is a SARS-CoV-2 variant derived from the recombinant variant XDV.1.5.1, with the earliest sample collected on 22 January 2025. NB.1.8.1 is one of six VUMs tracked by the WHO and was designated as a VUM on 23 May 2025 [1,2]. In comparison to the currently dominant SARS-CoV-2 variant, LP.8.1, NB.1.8.1 has the following additional Spike mutations: T22N, F59S, G184S, A435S, V445H, and T478I. When compared to JN.1, NB.1.8.1 has the following mutations: T22N, F59S, G184S, A435S, L455S; F456L, T478I, and Q493E.
Spike mutations at position 445 have been shown to enhance binding affinity to hACE2, which could increase the variant’s transmissibility, mutations at position 435 shown to reduce the neutralisation potency of class 1 and class 1/4 antibodies [3], and mutations at position 478 shown to enhance the evasion of Class 1/2 antibodies [4].
Using pseudoviruses and plasma from BA.5 breakthrough infections with JN.1 or XDV+F456Linfection, NB.1.8.1 showed 1.5–1.6-fold reduction in neutralization compared to LP.8.1.1 [4]. In mice previously immunized with SARS-CoV-2 variants, further immunisation using monovalent KP.2 or monovalent LP.8.1 mRNA vaccines elicited similar or modestly lower neutralising antibody titres against NB.1.8.1 than those elicited by immunising KP.2 or LP.8.1 antigens [5,6].
As of 18 May 2025, there were 518 NB.1.8.1 sequences submitted to GISAID [7] from 22 countries, representing 10.7% of the globally available sequences in epidemiological week 17 of 2025 (21 to 27 April 2025). While still low numbers, this is a significant rise in prevalence from 2.5% four weeks prior in epidemiological week 14 of 2025 (31 March to 6 April 2025), Table 1.
Between epidemiological weeks 14 and 17 of 2025, NB.1.8.1 increased in prevalence in all the three WHO regions that are consistently sharing SARSCoV-2 sequences, i.e. an increase from 8.9% to 11.7% for the Western Pacific region (WPR), from 1.6% to 4.9% for the Region of the Americas (AMR), and from 1.0% to 6.0% for the European Region (EUR). There are only 5 NB.1.8.1 sequences from the South East Asia Region (SEAR), and none from the from the African Region (AFR) and the East Mediterranean Region (EMR).

(Continue . . . )

Since 90% of the world's countries no longer reliably report COVID statistics (hospitalizations, deaths, etc.), it becomes increasingly difficult to evaluate the impact of emerging COVID strains (see No News Is . . . Now Commonplace).

This WHO TAG-VE report bases its assessment on 3 criteria (see below), in all of which they cite only low confidence in the data.

* Growth advantage Level of risk: Moderate, as NB.1.8.1 is growing substantially across all WHO regions with consistent SARSCoV-2 sequence data sharing.
Confidence: Low, as NB.1.8.1 expansion has only begun recently, there are low levels of sequencing data and therefore variant proportions exhibit spikes, and the variant has not been detected in some regions.
** Antibody escape Level of risk: Low, as the immune evasion of NB.1.8.1 in available data is of a similar magnitude to prior JN.1 sublineages upon their emergence. Additionally, NB.1.8.1 clusters with other JN.1 sublineages within antigenic cartography data based on sera from immunised mice.
Confidence: Low, as NB.1.8.1 antigenicity has only been assessed in a single study using pseudoviruses with serological data from two cohorts. Additional laboratory studies using sera from different cohorts and regions are needed to further assess the risk of antibody escape.
*** Severity and clinical considerations Level of risk: Low, as currently there are no reports of elevated disease severity associated with this variant. Available evidence doesn't suggest resistance to Nirmaltevir.
Confidence: Low. Currently there are no studies assessing the impact of this variant on clinical outcomes. Although, there is regular co-ordination and data sharing between all WHO Regional Offices, countries, and partners, reporting of new hospitalizations, ICU admission data with the WHO has been decreased substantially, therefore caution should be taken when interpreting trends in routine surveillance of severe cases. No studies have been conducted yet on the potential impact of the variant on the activity of antivirals like remdesivir and molnupiravir.

The global decision 2+ years ago to stop - or severely limit - the collection and sharing of COVID data may have been politically or economically expedient, but it has left us vulnerable to being blindsided by the next COVID variant of concern (VOC).