August 6, 2020

expert reaction to Part 2 of the REACT-1 study on coronavirus spread across England (preprint)

A preprint, an unpublished non peer-reviewed study posted on the Imperial College London website, looked at the spread of COVID-19 across England. 

This Roundup accompanied an SMC Briefing

Prof Paul Hunter, Professor in Medicine at the University of East Anglia, said:

“The value of the REACT-1 study is that it takes swabs from a random sample of the UK population. Consequently, it should give a less biased indicator of the prevalence of infection than the pillar two testing which is primarily done on people who request a test because of the presence of symptoms.

“However, such population sampling is not free of bias as different sections of society may be more or less likely to volunteer to participate. Where such differences in volunteering are correlated with risk (ethnic groups, people living in deprived areas) as is likely for COVID-19 this could lead to bias. Nevertheless, assuming that such biases remain constant over time, this study will provide a valuable retrospective analysis of trends in incidence across the country.

“The primary conclusion from this study was that there was a decline in prevalence between the first round (May) and the second round (19th June – 8th July) and within both rounds one and two. This finding is flagged up in the government press release ‘Largest testing programme for coronavirus shows virus continued to decline in June’.

“This finding is not surprising as it fits exactly with the reports of pillar 2 testing positive results that are reported each day. There is general agreement that the relaxations in lockdown restrictions in early June were not sufficient to push the R value above 1. The REACT-1 study has shown that the rate of decline had slowed between round 1 and 2 suggesting that the relaxations in early June did allow the R value to drift up. The study does not enable any conclusions to be drawn about what impact any of the further relaxation from late June onwards may have had. Indeed, it is likely that the impact of any relaxation will not be seen in swab data for at least a week or two after implementation. The fact that pillar 2 reports are increasing does raise concerns that the R value has increased above 1 at least in some parts of the country. The big uncertainty at present is how much of the increase in pillar 2 positive reports is due to a real increase in infections and how much to increased testing. We will need to await the results of REACT-1 round 3 to be able to answer this.

“In conclusion, this report largely confirms what we already know about the trajectory of the epidemic in England. But it is important to realise that the fact that the early relaxations in June did not cause an increase in cases does not mean that further relaxations will have done so already or will do so in the future.”

https://www.imperial.ac.uk/medicine/research-and-impact/groups/react-study/

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

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.