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Quantifying the impact of physical distance measures on the transmission of COVID-19 in the UK
Amy Gimma
Kiesha Prem
CMMID COVID-19 working group
Petra Klepac
G James Rubin
W John Edmunds
Christopher I Jarvis
Kevin Van Zandvoort
Novel Coronavirus
Acceso Abierto
Background: To mitigate and slow the spread of COVID-19, many countries have adopted unprecedented physical distancing policies, including the UK. We evaluate whether these measures might be sufficient to control the epidemic by estimating their impact on the reproduction number (R0, the average number of secondary cases generated per case). Methods: We asked a representative sample of UK adults about their contact patterns on the previous day. The questionnaire documents the age and location of contacts and as well as a measure of their intimacy (whether physical contact was made or not). In addition, we asked about adherence to different physical distancing measures. The first surveys were sent on Tuesday 24th March, one day after a “lockdown” was implemented across the UK. We compared measured contact patterns during the lockdown to patterns of social contact made during a non-epidemic period. By comparing these, we estimated the change in reproduction number as a consequence of the physical distancing measures imposed. We used a meta-analysis of published estimates to inform our estimates of the reproduction number before interventions were put in place. Findings: We found a 73% reduction in the average daily number of contacts observed per participant (from 10.2 to 2.9). This would be sufficient to reduce R0 from 2.6 prior to lockdown to 0.62 (95% confidence interval [CI] 0.37 - 0.89) after the lockdown, based on all types of contact and 0.37 (95% CI = 0.22 - 0.53) for physical contacts only. Interpretation: The physical distancing measures adopted by the UK public have substantially reduced contact levels and will likely lead to a substantial impact and a decline in cases in the coming weeks. However, this projected decline in incidence will not occur immediately as there are significant delays between infection, the onset of symptomatic disease and hospitalisation, as well as further delays to these events being reported. Tracking behavioural change can give a more rapid assessment of the impact of physical distancing measures than routine epidemiological surveillance. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This project was funded by the European Union’s Horizon 2020 Research and Innovations Programme - project EpiPose (Epidemic Intelligence to Minimize COVID-19’s Public Health, Societal and Economical Impact, No 101003688). CIJ and AG were funded by the Global Challenges Research Fund (ES/P010873/1). KvZ (Elrha’s Research for Health in Humanitarian Crises [R2HC] Programme, UK Government [Department for International Development], KP was funded by the National Institute for Health Research (NIHR; 16/137/109). PK was funded by the Bill & Melinda Gates Foundation (INV-003174). GJR was funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Emergency Preparedness and Response at King’s College London in partnership with Public Health England (PHE), in collaboration with the University of East Anglia and Newcastle University. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health and Social Care or Public Health England Megan Auzenbergs and Kathleen O'Reilly (Bill and Melinda Gates Foundation, OPP1191821); Graham Medley (NTD Modelling Consortium by the Bill and Melinda Gates Foundation (OPP1184344); Jon C Emery and Rein M G J Houben (European Research Council Starting Grant, Action Number #757699); Nicholas Davies (NIHR HPRU-2012-10096); Emily S Nightingale (Bill and Melinda Gates Foundation, OPP1183986); Wellcome Trust, and NIHR); Stefan Flasche (Sir Henry Dale Fellowship 208812/Z/17/Z); Thibaut Jombart (Research Public Health Rapid Support Team, NIHR Health Protection Research Unit Modelling Methodology); Joel Hellewell, Sam Abbott, James D Munday, Nikos I Bosse and Sebastian Funk (Wellcome Trust 210758/Z/18/Z); Fiona Sun (NIHR; 16/137/109); Akira Endo (The Nakajima Foundation; The Alan Turing Institute); Alicia Rosello (NIHR: PR-OD-1017-20002); Simon R Procter (Bill and Melinda Gates Foundation, OPP1180644); Fiona Sun (NIHR; 16/137/109); Adam J Kucharski and Timothy W Russell (Wellcome Trust, 206250/Z/17/Z); Gwen Knight (UK Medical Research Council, MR/P014658/1); Hamish Gibbs (Department of Health and Social Care ITCRZ 03010); Quentin Leclerc (Medical Research Council London Intercollegiate Doctoral Training Program studentship (grant no. MR/N013638/1); Billy J. Quilty, Charlie Diamond, Yang Liu and Mark Jit National Institute for Health Research NIHR; 16/137/109). Yang Liu and Mark Jit (Bill & Melinda Gates Foundation INV-003174); Samuel Clifford (Sir Henry Dale Fellowship 208812/Z/17/Z); Carl A.B. Pearson (NTD Modelling Consortium by the Bill and Melinda Gates Foundation OPP1184344); Rosalind M. Eggo (Health Data Research UK MR/S003975/1); Arminder K Deol; This research was partly funded by the NIHR (16/137/109) using aid from the UK Government to support global health research. The views expressed in this publication are those of the author(s) and not necessarily those of the NIHR or the UK Department of Health and Social Care. ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The data for the contact matrices will be made available in the coming days.
Cold Spring Harbor Laboratory Press
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