XBB.1.9.1 – a new variant of concern? – 4 updates

Australia, Austria, Coronavirus, Deaths, Denmark, Elderly, England, Europe, France, Genome, Germany, Hospitalization, Indonesia, Infection, Recombination, Singapore, South Africa, Testing, Transmission, UK, XBB.1.9.1

XBB.1.9.1, a new recombinant subvariant that is suddenly cropping up across the globe, is causing some concern amongst epidemiologists.

Let’s start with the UK, where XBB.1.9.1, according to Covspectrum, is already at nearly 12% of sequences.

The UK Health and Security Agency have recently published a technical briefing giving details of variants causing concern. This is what the technical briefing has to say about XBB.1.9.1:

XBB.1.9.1 is rapidly increasing in proportion and is currently the only lineage with a significant growth advantage relative to XBB.1.5, though with small numbers identified.

As of 7 March 2023, 1,168 XBB.1.9.1 sequenced cases had been identified in England. There were 39 deaths among these cases.*

The median age of cases was 72 years old. The majority of cases were female (611), with 430 male cases (Figure 12). There have been cases in each region of England with the most cases resident in the Yorkshire and Humber (205) and East of England (195) (Figure 13). Care home residents comprised 25.3% (296 out of 1,168) of XBB.1.9.1 cases, a similar proportion to all sequenced cases.

(* our emphasis)

That is an extraordinarily high fatality rate at this point in the pandemic.

The full UK Technical Briefing 51 is republished below. The comments above come from page 23.




UKHSA Technical Briefings


In Singapore, where XBB.1.9.1 comprises about 12% of sequences, hospitalizations seem to be increasing:

There is also a recent increase in Singapore ICU cases:


In the Netherlands, XBB.1.9.1 is just starting to appear in the variant mix, but Dutch hospitalizations are at a high not seen since October 2022.


In France, a new Covid wave seems to be gathering pace, with XBB,1.9.1 currently as small part of the mix:


But there are some extraordinary new Covid figures from France today:


In Indonesia, XBB.1.9.1 now has a share of more than 50% of its variants


And wastewater specialist Marc Johnson predicts that XBB.1.9* will overtake XBB.1.5

Ryan Hisner believes XBB.1.16 could be a stronger candidate to supersede XBB.1.5 than XBB.1.9.1


This latest chart from Regeneron for the UK seem to suggest that XBB.1.9.1 has put a brake on further growth of XBB.1.5. 



XBB.1.9.1 has recently been spotted in two sequences from China:


XBB.1.9.1 Growth Rate in the United States.

These two tables show the growth rate of XBB.1.9.1 over just ONE WEEK in the US.



UK: XBB.1.5 compared to XBB.1.9.1

XBB.1.9.1 outcompetes XBB.1.5 before the end of March 2023 by the look of it. (XBB.1.9.1 in green.)


UPDATE 1 – 24th March 2023 – XBB.1.9.1 now at 6.1% of global sequences


XBB.1.9.1 is already the second most common variant sequenced globally


Regeneron is showing that XBB.1.9.1 was at 8% of global sequences on 6th March 2023. If the XBB.1.9.1 variant is doubling every two weeks or so, then the current total could already be 16% – 20% of all sequences globally.


covSpectrum comparing the growth of XBB.1.5, XBB.1.9.1, and XBB.1.16.

On March 12th 2023, XBB.1.5 was at ~72% of global sequences. Less than two weeks later, it’s around 40%.




UPDATE 2 – 25th March 2023 – Latest charts from Australian researcher Mike Honey shows XBB.1.9.1 and XBB.1.9.2 both increasing in the US, with a potential crossover with XBB.1.5 in April 2023:


Mike Honey on Aus.social


Update 3 – 27th March 2023 – XBB.1.9.1 set to overtake XBB.1.5 in Victoria, Australia

Mike Honey on Twitter



UPDATE 4 – 31st March 2023 – XBB.1.9.1 gaining ground in South Africa.

South Africa is seeing some growth in the XBB.1.9.1 variant – particularly in the province of Gauteng.

CovSpectrum is showing XBB.1.9.1 at between around 18% AND ~24% of sequences, but these results are from very low sequence numbers


Regereron suggests that almost all the new XBB.1.9.1 infections in South Africa are in the Gauteng province:

Note: these predictions are based on very low sequence numbers


We will be updating this thread with further news about XBB.1.9.1 as it breaks..



The world’s first XBB wave begins in Singapore





** This post was originally published on March 11, 2023 **