With new analyses showing lower severity for Omicron cases, what will this mean for our projections? Well obviously this will tend to bring the numbers lower, which is great — but I want to clear up a few misconceptions.

https://twitter.com/BarnardResearch/status/1469646833563615237

There was some confusion over what our models, which assumed Omicron had equal "baseline" severity to Delta, meant for severity in practice. This leads to around a 40% reduction in realised severity within each age group, because more Omicron cases are breakthrough/reinfections.

COVID-19 surveillance, England. The most recent 5 days (to 28 Nov) show an increase in S gene target failure in community testing data. An explainer follows. 🧵 But before I go on, I will remind my scientific and media readers that SGTF is only a proxy for Omicron, and is also found in other SARS-CoV-2 lineages. Lineage identity can only be confirmed by sequencing, and longer-term surveillance is required to establish any trend.

Our paper “Increased mortality in community-tested cases of SARS-CoV-2 lineage B.1.1.7” is in Nature today. We find that B.1.1.7, the UK coronavirus variant identified in late 2020, is associated with 55% higher COVID-19 mortality than other lineages. nature.com/articles/s4158… 1/16 The LSHTM team has been analysing B.1.1.7 for signs of increased or decreased severity since late December. We first identified a signal of higher mortality in mid-January. This led to an announcement by the PM and @uksciencechief on 22 January. bbc.co.uk/news/health-55… 2/16

Our paper “Estimated transmissibility and impact of SARS-CoV-2 lineage B.1.1.7 in England” has now been published in Science (early release: science.sciencemag.org/content/early/…). I’ve tweeted about this a few times before, so I’m going to focus here on some key messages. (1/8) B.1.1.7 has a 43–90% higher reproduction number than previous SARS-CoV-2 strains. This holds for several different methods we used to analyse its spread, and we found similar rates of increase in the UK, Denmark, Switzerland, and the United States. (2/8)

We've updated our preprint on the transmissibility of SARS-CoV-2 VOC 202012/01, aka B.1.1.7, with new statistical and modelling methods. Headline: we estimate VOC is 43–82% more transmissible than preexisting variants. UNDER PEER REVIEW cmmid.github.io/topics/covid19… (1/6) We now include new statistical estimates of B.1.1.7 growth, which accord with our earlier model-based estimates—and provide some really interesting plots. (thanks @Alex_Washburne, @inschool4life, @TWenseleers, @seabbs and @sbfnk!) UNDER PEER REVIEW (2/6)

@i_petersen Thanks Irene. See image, sorry for bad labelling! Essentially the major pattern is that it doesn't seem to have spread into 80+ quite as quickly. Over November, 0-19s were slightly overrepresented but that seems to have somewhat settled out now. (1/2) @i_petersen UK scientists originally interpreted this as the variant spreading (slightly) more easily among children than preexisting variants. But with newer data now in, this may have just been a transient effect related to schools being open during the November lockdown. 2/2

I can present a brief update to our analyses of VOC 202012/01 from last week. VOC 202012/01 continues to spread in England, as shown in both sequencing data from COG-UK and Pillar 2 testing data provided by Public Health England. NOT PEER REVIEWED 1/7 While the sequencing data above are definitively VOC 202012/01, S-gene target failure (SGTF) is also associated with some other lineages. However, PHE estimates some 98% of SGTF are now VOC 202012/01 (assets.publishing.service.gov.uk/government/upl…). NOT PEER REVIEWED 2/7

Just to comment on a few points that have come up in relation to the preprint we put out yesterday on VOC 202012/01, the new variant of SARS-CoV-2 in the UK. (

https://twitter.com/_nickdavies/status/1341845176361349123?s=20

) Is the apparent spread of VOC due to increased testing? This comes up often when cases rise & indeed case data is subject to biases. But we don't fit to case data in the model. Hospitalisations, deaths, and relative frequency (not abs. number) of the new variant define the trend.

Late last week, it was announced that a new variant of SARS-CoV-2 (VOC 202012/01) was detected and appeared to be spreading rapidly in the south east of England. We analysed the transmissibility and severity of this new variant. [cmmid.github.io/topics/covid19…] NOT PEER REVIEWED 1/9 We fitted a mathematical model to the growth of VOC 202012/01 in these three regions of England. If current trends continue, the new variant could represent 90% of cases by mid-January. NOT PEER REVIEWED 2/9