April 1, 2020

expert reaction to preliminary estimates that the reproductive number in the UK during the lockdown may be below 1

A non peer reviewed report into the reproductive number of COVID-19 in the UK, has found that it may have lowered to below 1 during the nation wide lockdown. 

Prof Brendan Wren, Professor of Microbial Pathogenesis, London School of Hygiene & Tropical Medicine, said:

“The preliminary study based on a large cohort of 1,356 UK adults suggests that the reproduction number can be decreased from 2.6 to approximately 0.62 through social distancing. This is encouraging and suggests that social distancing and hygiene measures can in time cut off the number of people that the SARS-Cov-2 virus can infect. The study is based on behavioural change which is a “quick and easy way” of estimating the SARS-Cov-2 virus reproduction number, which is very useful, but would need to be validated by independent traditional methods like community testing.”

Dr Jennifer Cole, Biological Anthropologist, Royal Holloway, University of London, said:

“This is an extremely valuable study that not only looks at behaviour in general but also takes into account that different types of contact, such as whether or not skin-to-skin contact was made, will affect transmission. It is also valuable that the numbers of contacts made are measured against a known baseline from before the current lockdowns were implemented, thereby identifying how much less contact is occurring. The results show that the physical distancing measures that have been put in place appear to have reduced the R0 – the number of people each infected person passes the disease on to – to below 1. Once the R0 is below 1, the disease will eventually peter out. How quickly depends on how far below 1 the rate can be pushed. It is important to remember that cases will still rise in the short-term as people who were already infected before the lockdowns were implemented may not yet have developed symptoms.

“It is also valuable that this study shows that R0 can be reduced significantly even when people are still allowed to go out for essential food and medicines and with essential workers still operating: the vast majority of the skin-to-skin contacts recorded in the study were between family members in the home, not while out shopping or working. Avoiding handshakes, air kisses and so on between those who are still working at this time is extremely important. As further data comes through in the coming weeks, the value of physical distancing, and of behaviour in general, will be even better understood but this study shows clearly the important role everyone can play in ensuring COVID19 can be overcome.”

Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said:

“This study is showing the reduction in social mixing that has occurred for most people since restrictions were put in place.  As for any research projects like this, the representativeness of this population studied is crucial. Market research companies are very good at this but being email based part of the population could not be included, particularly the elderly, but this group has been asked to self isolate for their own protection.  Their findings in the reduction of contacts is similar to reductions that occurred in Wuhan.  An important factor is that in lockdown you may be meeting 2-3 contacts a day but they are largely the SAME contacts further limiting the potential for ongoing transmission.

“The degree of contact included here which included just a quick conversation with someone is very inclusive of all contacts.  Risk is obviously greater with greater degrees of contact.

“Given the flattening in new cases and we have some measures in place now for over 2 weeks and a type of lockdown for over 1 week, their conclusion that R0 may be below 1 is credible.  Once R0 is below 1 the epidemic cannot sustain itself as each case produces less than one new case and the epidemic eventually ceases.

“This does not provide any evidence for how long we need to continue lockdown but similar studies could be done to look at the social mixing patterns if they are partially relaxed.  A number of countries held up as being good models are allowing restaurant and bars to be open but with operating restrictions on numbers and how far tables are apart.”

The Impact of physical distance measures on transmission in the UK: https://cmmid.github.io/topics/covid19/current-patterns-transmission/comix-impact-of-physical-distance-measures-on-transmission-in-the-UK.html

All our previous output on this subject can be seen at this weblink: www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.