July 28, 2021

expert reaction to latest daily case numbers

Some comments from scientists on the latest figures on the DHSC COVID-19 Dashboard.

Prof Carl Heneghan, Centre for Evidence-Based Medicine and Nuffield Department of Primary Care Health Sciences, University of Oxford, said:

“I focus on three measures in England’s data to assess the change in the epidemic  (You can use the same method for the other nations, regions or Local authorities)

1. Specimen date
2. Daily change in reported cases by specimen date
3. Weekly number of people receiving a PCR test and positivity

1. The specimen date. 

• Cases by specimen date peaked in England on the 15th of July (56,266). 
• The time to reporting of positive tests has improved over time and therefore use the specimen data from 4 days previous as a fairly reliable measure. On the 24th of July, there were 18,779 cases.
• However, there are often lower figures on the weekends (17th, 18th and 24th, 25th) and a rebound on Monday, which is reflected in today’s  reporting increase – (see table 1 at the end), 

2. The data in England on the ‘Daily change in reported cases by specimen date’ provide a sensitive measure for assessing changes to previously reported cases. (see link here) 

• As an example, comparing the 27th (5,946 cases) with the previously days reported cases on the 26th (6,565) suggest the trend is still on a downward trajectory.
  
  

3. Finally, the testing data provides the weekly number of people receiving a PCR test and positivity. 

• PCR positivity is 10.2% on the 23rd from a peak of 11.8% on the 19th. (see here)

These three measures taken together show the epidemic is currently in decline. 

Table 1, Specimen date in England 

Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“While it is never encouraging to see infection numbers rise, it should be seen against a week of consistent decline.  On the other hand, it could be the very first signs of increasing infections in response to the ending of restrictions on 19 July.  It is always unwise to pin too much importance on a few days data, and using 7 day’s worth of numbers to diagnose the end of Covid in the UK, as some people have done, is absurd.  Turnaround in case numbers can and does occur very abruptly, as we have seen around the world.

“The virus’ spread over the summer will be determined by people’s patterns of behaviour.  It remains the case that mixing of people will remain the most significant driver of infection numbers, while vaccinations will have the largest effect to reduce those numbers.  Of course, the vaccines are not 100% effective at reducing transmission, and the virus cannot spread at all without social interactions, so ongoing care needs to be taken while numbers are still high.”

Prof James Naismith, Director of the Rosalind Franklin Institute, and University of Oxford, said:

“The good news is week to week, the number of cases detected by testing (test positives) has fallen. We should be careful not to rely on day to day fluctuations in these numbers to judge what is happening the June / early July wave (that is pre 19th July). Scientists cannot reliably draw conclusions on these noisy data.

“What we need to know is the trend in

(1) How many people and what is age / vaccine status of the infected?

Positive test cases are one way to estimate this but I remain convinced that the most important data at the moment with which to judge the progress of this wave are the ONS survey results.

However, they are a lagging indicator.

(2) How many people are admitted to hospital with severe covid19? This is less than and lags the number of cases.

Provided the government has not changed the basis of the derivation of this number, this tells us about the pressure on the NHS.

(3) How many people are suffering from long covid and how long does this last?

This is not well measured but can tell us about the human suffering.

(4) How many people are dying and their age / vaccine status? This is less than and lags the number of hospitalisation.

This measures the tragic human loss. Vaccines have massively changed the equation that relates these data. It takes many many more cases to produce a given number of hospitalisations. I am certain we will not see the toll we saw at the start of this year due to vaccines.

“In summary, today’s small rise tells us as much as the previous day’s small fall; precisely nothing. I am hopeful but do not know that the pre 19th July wave has peaked.

“It remains far too early to infer the effect of the ending of the lockdown on the test positives. It will be the end of this week or the start of the next before this begins to happen and it will be the third week in August before we have ONS data that really settles the matter. I would expect the end of lockdown (post 19th July) to result in a rise in cases.

“As a wider point, it is dispiriting to see selective switching focus between cases, test positives, hospital admissions and deaths to make confident pronouncements as political points. The public who have seen awful losses of loved ones and / or have had their lives blighted by restrictions deserve better. I would urge a lot more empathy, consistency and humility all round.

“There are many things happening at once, increased vaccination, school closure, increased outdoor time, warmer weather and changes in people’s behaviour. This make reliable prediction hard.

“We can make a difference today by

(1) Helping a vaccine hesitant person make the right decision for themselves; vaccines are safe and effective.

(2) Be outdoors where we can

(3) Improve ventilation in indoor spaces

(4) Wash our hands

(5) Wear a mask where we can’t keep 2m apart.

Dr Benjamin Neuman, Professor of Biology and GHRC Chief Virologist, Texas A&M University, said:

“One bad day does not make a trend, but the increasing number of new COVID cases certainly bears watching.  It takes several days from exposure to a first positive test – more so, when an at-home test needs to be reconfirmed – and all of this means that new case numbers tend to lag a week or so behind infections.  This increase is timed about right to be associated with Freedom Day, but there is not enough data to conclusively determine its cause at this time. 

https://coronavirus.data.gov.uk/

All our previous output on this subject can be seen at this weblink:

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.