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The record of the discussion that took place at SAGE’s ninety-ninth meeting has been published.
Prof Paul Hunter, Professor in Medicine, UEA, said:
“The situation update from SAGE contains relatively little that we did not know or was widely leaked earlier today.
“The key point is that the situation remains unclear, not least because of the lag between what is happening now and data becoming available to inform decision making. Although there may be ways for reducing it there will always be a lag between someone getting infected and then becoming ill, having a test, and that sequenced to determine whether it is due to omicron or delta. Also there is an inevitable lag between someone developing symptoms and their clinical condition deteriorating to the point that they need admission to hospital, which is why hospital admissions usually follow initial diagnosis by a week or two.
“If the current rate of doubling which is about every 2 days or even less continues, that would lead to scarily high numbers of infections each day very quickly. From the UK data summary there were 91,956 positive samples on the 14th December and from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1042221/20211218_OS_Daily-Omicron-Overview.pdfabout on the 14th December about 57% were s gene target failure samples (likely omicron variant). This suggests on the 14th December 57% of 91,956 total positives or about 52,000 positive omicron cases. Less than half of all infections are ever diagnosed so that would mean on 14th December there were most likely in excess of 100,000 new omicron infections. If that number doubled every day by New Year’s day that would mean over 50 million infections per day – clearly that is impossible, so the rate of increase has to start slowing soon. The question really is when and how rapidly this rate of growth will start to slow and how that will be affected by any further implementation of control measures.
“The only model of the trajectory of the omicron epidemic that I am aware of comes from John Edmunds’ group at the LSHTM and when published there were significant uncertainties in some of the key assumptions. It seems to me that the growth in cases over the past couple of weeks has been more rapid than suggested by the model. But as yet the increase in infections have been most obvious in London and the South East and in younger adults especially amongst 20 somethings. Whilst there is still debate over how much less (or possibly more) likely omicron is to put people in hospital, we do know that one of the biggest risk factors for hospitalisation with covid is a person’s age and to a large extent the pressure on the NHS will be more influenced by the age distribution of people being infected than uncertain difference in virulence between delta and omicron. How rapidly omicron will spread into older age groups, especially considering high rates of booster uptake in the over 60s, is still uncertain, at least to me. Nevertheless, unless we see significant slowing in the rate of growth over the next week – always a possibility – implementation of control measures later will likely have only a small impact of the overall infection rate.
“The other issue that does not seem to have been addressed is the relationship between the size of the spike in cases and the duration of the epidemic wave. As Professor Witty commented this week, in general epidemics that lead to a very rapid rise in case numbers to high numbers because they are highly transmissible are expected to be followed by a relatively rapid fall. Supressing the peak of an epidemic by non-pharmaceutical interventions such as lockdowns almost inevitably extends the duration of the epidemic. It is not clear from the sit rep that this was considered. Essentially, is it better to have a shorter but intense period of pressure or a less intense but longer period of increased demand?
“So the Sit Rep from SAGE gives us some indication of the way its members are thinking but doesn’t give many clear answers to the key questions facing the UK government at present.”
Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:
“To adjust for reporting delays, nowcasting in December 2021/January 2022 of hospital admissions for COVID-19 is as essential as it was in the initial wave in spring 2020. Nowcasting requires information on both date of hospital-admission and date of reporting-in of that hospital-admission. Reporting-delays are inevitable but can be managed down – even in a crisis – as they were in wave 1. The SPI-M-O modelling teams should and will have access to both dates so that they can work effectively and efficiently.”
Prof Ewan Birney, Deputy Director General of EMBL, and Director of EMBL’s European Bioinformatics Institute, said:
“The SAGE minutes and SPI-M models released today are sobering reading. Even with the strong booster campaign Omicron has to be very significantly less severe than Delta to not likely overwhelm healthcare capacity levels. Data from South Africa is interesting and positive about some lower severity of Omicron, but not obviously clear cut that it is at the levels needed. Furthermore, the South African pandemic experience is different in terms of demographics and previous infection wave, complicating the ability to extrapolate to the UK. Frustratingly it is likely that the time for a decision to take mitigating actions will be at the same time if not before a firm understanding of severity in an European setting. Commentors should watch carefully the situation in both London and Copenhagen hospitals where Omicron is high and there is good, prompt, public data analysis. An additional complication if unmitigated growth is accepted is the high levels of infection affecting healthcare workers, greatly complicating NHS staffing.
“The UK Government should be applauded for its prompt action on omicron including the increase of intensity of the booster campaign, free lateral flow tests, prompt, public data release and analysis and its preparation of the NHS. However, it seems likely that more action will be needed to get us through the Omicron wave, and, annoyingly for decision makers, such decisions are likely to be needed to be made in advance of conclusive evidence.”
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Prof Ewan Birney: “I am a consultant and shareholder for Oxford Nanopore, which makes DNA sequencing machines and I was on the Oxford/AstraZeneca clinical trial for the vaccine.”
None others received.