New variant Covid-19: why previously effective lockdown measures are no longer enough

The UK now tops the global league table of both new cases and new deaths from Covid-19. An in-depth regional analysis from within the UK, in research made available yesterday, has shone a light on the impact of the new variant on the spread of the infection.  These new data show why more stringent measures may be needed to control the pandemic with this new strain: which has now spread worldwide.  

UK’s sad position 

  • Global league tables need to be interpreted with caution and countries vary in how they capture and record new cases from Covid-19
  • The more testing there is and the more assiduous the follow up of contacts, the greater the number of cases identified 
  • However, it seems very compelling that the UK in the past few days has recorded a higher rate of new cases of Covid-19 than any other country for which  I can find data
  • The UK similarly leads the global ranking in the average number of deaths (per million) over the past few days
  • Again, the definition of what counts as a Covid-19 death varies and the recent holiday period means that national data records are subject to some delays

Recap about the new strain

  • Although first identified in November, it probably emerged first in September 2020 in the South East of England
  • There are a large number of genetic differences between this new strain and all previous strains
  • The major difference with this strain is that it changes the properties of the spike protein of the virus, allowing the virus to enter human cells more easily and multiply itself
  • It is thus more likely to be transmitted from one person to another 
  • As a result of these properties it has become the dominant strain in much of England
  • It has now been identified in 32 other countries:

Imperial College Report

  • A research report was published yesterday from Imperial College analysing the data accrued from the detailed genetic testing of 50000 virus samples in England
  • With this data the research was able to chart the growth of the variant and how it has contributed to the recent surge of cases in the UK

How quickly has this variant become the dominant strain?

  • As reported widely in the press both in UK and overseas, the new variant is spreading very rapidly
  • The Imperial College report now estimated that across the whole of England the R number is:
    • 1.45 for the new variant 
    • 0.92 for the old variant
  • The research also estimates that the doubling time (ie how long does it take for the number of cases to double) could be as short as 3.7 days
  • Further analyses showed there was no evidence that this new variant has a shorter incubation period.  ie it is not more transmissible because people get ill quicker
  • There was an effect of age with proportionately more younger people testing positive with the new variant – although this was only part of the story – but the differences were modest 
  • The key finding is the in-depth analysis by region
  • Below I reproduce the figures from the Imperial report for the 3 most affected regions
  • The different colours show the increasing proportion of cases in these 3 regions 
    • Green dots are London
    • Brown dots are Eastern counties
    • Blue dots are South Eastern counties

*for the mathematically inclined the numbers on the vertical axis are expressed as logs!

  • The patterns of dots all show the exponential rise in this variant as a proportion of all cases in these regions
  • This was not the cases in all regions (up to now)
  • Indeed, during this 7-week period some regions of England showed substantial decreases
  • Before the new variant was identified, these differences between regions in their  time trends were difficult to explain 
  • The Government progressively introduced stricter lockdown rules which had been successful in some areas but not others
  • This now seems to be related to the emergence of the new strain
  • However, the proportion of cases due to the new variant is increasing in all in the different regions of England but the regional analysis has important policy implications

A tale of 2 regions: 

I will illustrate the point by focusing on 2 very different parts of England

(1.) Humberside.

  • Humberside is in the Northeast of England 
  • This is a graph plotting the number of cases in that region between weeks 44 and 50 of the year 2020
  • The thick line on the graph shows how the number of cases declined in the last couple of months from around 6000 per week to over 2000 now
  • Most cases had not been tested for whether they were new variant or not
  • In those that were tested, almost all cases (thin turquoise line-labelled ‘S+’) were the ‘old’ variant.  There were no cases with the new variant (thin orange line-labelled ‘S-‘)
  • The two red vertical  lines indicate the timing of changes in government policy to a more stringent lockdown
  • Lockdown restrictions have brought down the number of cases substantially in a very short time period in a region with no new variant viruses

(2.) Kent

  • Kent is in the Southeast of England
  • Here we see a very different picture
  • Cases (the thick line*) grew from just over 2500 to around 8000 per week
  • Because of the interest in this region, more cases were tested for the new variant 
  • Most of the cases tested were due to the new variant (thin orange line) which parallels the trend in all cases
  • Very few of the new cases were due to the ‘old variant’ (thin turquoise line)
  • New cases grew substantially despite the increasing lockdown restrictions, which had no effect on the incidence of new variant Covid-19 

*This line varies in colour to show how the orange is taking over from the turquoise


  • The first conclusion is that this new variant has the capacity to spread very quickly and become the dominant strain
  • Its emergence in so many other countries has to be a cause for concern
  • Most telling is that lockdown measures that had controlled the spread of the ‘old variant’ seem to be inadequate to control the spread of the new variant 
  • The assumption has to be that only with more stringent measures than have been currently employed will bring the rates down
  • Just to emphasise again, there is still no reason to believe that the new vaccines will not protect against this new variant 

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3 replies on “New variant Covid-19: why previously effective lockdown measures are no longer enough”

Isn’t this classic natural selection? The virus has variants, and this new one has a stronger ability to infect. When lockdown reduces opportunities to find new hosts, the more infectious variant does better, reproduces more often, and becomes the dominant strain. Because it is more infectious, measures such as mask wearing, hand washing and social distancing might be less effective. If and when large quantities of vaccine are manufactured and used, hosts will become harder to find and this and future variants will be at R<1. Assuming that the vaccines still work…


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