Category Archives: Uncategorized

COVID-19: why did a second wave occur even in regions hit hard by the first wave?

By Nic Lewis

 Introduction

Many people, myself included, thought that in the many regions where COVID-19 infections were consistently reducing during the summer, indicating that the applicable herd immunity threshold had apparently been crossed, it was unlikely that a major second wave would occur. This thinking has been proved wrong. In this article I give an explanation of why I think major second waves have happened. Continue reading

The relative infectivity of the new UK variant of SARS-CoV-2

By Nic Lewis

Key points

  • A new variant, B.1.1.7, of the SARS-CoV-2 virus has recently spread rapidly in England
  • The public health agency’s best estimate of B.1.1.7’s weekly growth rate advantage is 1.51x
  • They mis-convert this in a reproduction number ratio of 1.47; converting appropriately gives a ratio of 1.25
  • Confident claims by the UK government scientific advisers that the higher growth of B.1.1.7 is due to increased transmissibility are misplaced; it could be partly of wholly due to other factors
  • 1.1.7 has not shown a greater growth rate advantage than two previous variants did, both of which are now thought to have no greater transmissibility than previously existing variants
  • There is little evidence that B.1.1.7 is more virulent, or likely to be resistant to existing vaccines

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Asymptomatic spread(?) of Covid-19

by Judith Curry

I just finished reading an article entitled Asymptomatic Spread Revisited. Continue reading

T cell cross-reactivity and the Herd immunity threshold

By Nic Lewis

An interesting new paper by Marc Lipsitch and co-authors, “Cross-reactive memory T cells and herd immunity to SARS-CoV-2”, has recently been published.[1] It discusses immunological and epidemiological aspects and implications of pre-existing cross-reactive adaptive immune system memory arising from previous exposure to circulating common cold coronaviruses. They argue that key potential impacts of cross- reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. I believe that they are mistaken on the herd immunity point, as I will show in this article. Continue reading

Herd immunity to COVID-19 and pre-existing immune responses

By Nic Lewis

I showed in my May 10th article Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. Continue reading

COVID-19: evidence shows that transmission by schoolchildren is low

By Nic Lewis

Much fuss has been made in the UK, not least by teachers’ unions, about recommencing physical school attendance. As this issue applies to many countries, I thought it worth highlighting research findings in Europe. Continue reading

Politics discussion thread

by Judith Curry

It’s time for a politics thread, to deflect the political comments that are sneaking into the technical threads.

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Cancel culture discussion thread II

by Judith Curry

Some additional articles and events to discuss.

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Why herd immunity to COVID-19 is reached much earlier than thought – update

By Nic Lewis

I showed in my May 10th article Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. I opined, based on my modelling, that the HIT probably lay somewhere between 7% and 24%, and that evidence from Stockholm County suggested it was around 17% there, and had been reached. Mounting evidence supports my reasoning.[1]

I particularly want to highlight an important paper published on July 24th “Herd immunity thresholds estimated from unfolding epidemics” (Aguas et al.).[2] The author team is much the same as that of the earlier theoretical paper (Gomes et al.[3]) that prompted my May 10th article. Continue reading

The progress of the COVID-19 epidemic in Sweden: an analysis

By Nic Lewis

The course of the COVID-19 pandemic in Sweden is of great interest, as it is one of very few advanced nations where no lockdown order that heavily restricted people’s movements and other basic freedoms was imposed. As there has been much comment, some of it ill-informed, on how the COVID-19 epidemic has developed in Sweden, but relatively little detailed analysis published in English, it is worth exploring what their excellent publicly-available data reveal. Continue reading

Did lockdowns really save 3 million COVID-19 deaths, as Flaxman et al. claim?

By Nic Lewis

Key points about the recent Nature paper by Flaxman and other Imperial College modellers

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Mass spectrometry and climate science. Part I: Determining past climates

by Roland Hirsch

Mass spectrometry is essential for research in climate science.

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Covid discussion thread: Part VIII

by Judith Curry

Interesting papers that I’ve recently spotted

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When does government intervention make sense for COVID-19?

By Nic Lewis

Introduction

I showed in my last article that inhomogeneity within a population in the susceptibility and infectivity of individuals would reduce the herd immunity threshold, in my view probably very substantially, and that evidence from Stockholm County appeared to support that view. In this article I will first provide other evidence pointing to such population inhomogeneity being very considerable. I will then go on to consider how the overshoot of infections beyond the herd immunity threshold could be reduced. Continue reading

Why herd immunity to COVID-19 is reached much earlier than thought

By Nic Lewis

Introduction

A study published in March by the COVID-19 Response Team from Imperial College (Ferguson20[1]) appears to have been largely responsible for driving government actions in the UK and, to a fair extent, in the US and some other countries. Until that report came out, the strategy of the UK government, at least, seems to have been to rely on the build up of ‘herd immunity’ to slow the growth of the epidemic and eventually cause it to peter out. Continue reading

A sensible COVID-19 exit strategy for the UK

By Nic Lewis

The current approach

A study by the COVID-19 Response Team from Imperial College (Ferguson et al. 2020[i]) appears to be largely responsible for driving UK government policy actions. The lockdown imposed in the UK appears, unsurprisingly, to have slowed the growth of COVID-19 infections, and may well soon lead to total active cases declining. However, it comes at huge economic and social costs, and substantial COVID-19-unrelated health costs.

Worse, the lockdown is merely a holding strategy, which offers no long term solution to the COVID-19 problem. The eventual total number of deaths for COVID-19 are not reduced relative to any less restrictive policy that likewise avoided the health system being overwhelmed. Deaths are merely spread over a longer period, assuming that eventually restrictions are lifted and people’s lives return to normal. Continue reading

CoV Discussion Thread III

By Judith Curry

My latest selection of interesting articles.

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Imperial College UK COVID-19 numbers don’t seem to add up

By Nic Lewis

Introduction and summary

A study published two weeks ago by the COVID-19 Response Team from Imperial College (Ferguson20[1]) appears to be largely responsible for driving UK government policy actions. The study is not peer reviewed; indeed, it seems not to have been externally reviewed at all. Moreover, the computer code used to produce the estimates in the study – which on Ferguson’s own admission is old, unverified and documented inadequately, if at all – has still not been published. That, in my view, shows a worrying approach to a matter of vital public concern.

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CoV discussion thread II

by Judith Curry

Time for a new thread.

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COVID-19: Updated data implies that UK modelling hugely overestimates the expected death rates from infection

By Nic Lewis

Introduction

There has been much media coverage about the danger to life posed by the COVID-19 coronavirus pandemic. While it is clearly a serious threat, one should consider whether the best evidence supports the current degree of panic and hence government policy. Much of the concern in the UK resulted from a non-peer reviewed study published by the COVID-19 Response Team from Imperial College (Ferguson et al 2020[1]). In this article, I examine whether data from the Diamond Princess cruise ship – arguably the most useful data set available – support the fatality rate assumptions underlying the Imperial study. I find that it does not do so. The likely fatality rates for age groups from 60 upwards, which account for the vast bulk of projected deaths, appear to be much lower than those in the Ferguson et al. study. Continue reading

Coronavirus technical thread

by Judith Curry

A thread devoted to technical topics, e.g. epidemiology, immunology, treatments.  A more general thread will be coming shortly.

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Coronavirus discussion thread

by Judith Curry

Discuss.

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Climate sensitivity in light of the latest energy imbalance evidence

by Frank Bosse

Equilibrium climate sensitivity computed from the latest energy imbalance data.

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Comment by Cowtan & Jacobs on Lewis & Curry 2018 and Reply: Part 2

By Nic Lewis

In an earlier article here I discussed a Comment on Lewis and Curry 2018 (LC18) by Kevin Cowtan and Peter Jacobs (CJ20), and a Reply from myself and Judith Curry recently published by Journal of Climate (copy available here). I wrote that I would defer dealing with the differences between observed and CMIP5 model-simulated historical warming, which formed the basis of CJ20’s numerical analysis, until a subsequent article. I now do so. Continue reading

Gregory et al 2019: Unsound claims about bias in climate feedback and climate sensitivity estimation

By Nic Lewis

The recently published open-access paper “How accurately can the climate sensitivity to CO2 be estimated from historical climate change?” by Gregory et al.[i] makes a number of assertions, many uncontentious but others in my view unjustified, misleading or definitely incorrect.

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