Quantifying the impact of physical distance measures on the transmission of COVID-19 in the UK

AbstractBackgroundTo 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).MethodsWe 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.FindingsWe 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.InterpretationThe 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.Research in contextEvidence before this studyMany governments have adopted physical distancing measures to mitigate the impact of the COVID-19 pandemic. However, it is unclear to what extent these measures reduce the number of contacts and therefore transmission. We searched PubMed and medRxiv on March 28, 2020, with the terms “ (coronavirus OR COVID-19 OR influenza) AND ((school OR work) AND (closure OR holiday)) AND (contact OR mixing)” and identified 59 and 17 results, respectively. Only one study conducted in China during the COVID-19 pandemic reported a reduction in daily contacts outside the home during the period of “ lockdown”. We found no other published articles that empirically quantify the impact of these measures on age- and location-specific mixing patterns.Added value of this studyBy surveying adults’ behaviour in the UK during a period of stringent physical distancing (“ lockdown”) and comparing the results to previously collected data, we found a large reduction in daily contacts particularly outside the home, resulting in a marked reduction in the estimated reproduction number from 2.6 to 0.62 (95% bootstrapped confidence interval [CI] 0.37 - 0.89). This method allows for rapid assessment of changes in the reproduction number that is unaffected by reporting delays.Implications of all the available evidenceChanges in human contact behaviour drive respiratory infection rates. Understanding these changes at different stages of the COVID-19 pandemic allows us to rapidly quantify the impact of physical distancing measures on the transmission of pathogens.

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Modelling the impact of the tier system on SARS-CoV-2 transmission in the UK between the first and second national lockdowns

BMJ Open ◽

10.1136/bmjopen-2021-050346 ◽

2021 ◽

Vol 11 (4) ◽

pp. e050346

Author(s):

Daniel J Laydon ◽

Swapnil Mishra ◽

Wes R Hinsley ◽

Pantelis Samartsidis ◽

Seth Flaxman ◽

...

Keyword(s):

Real Time ◽

Reproduction Number ◽

Secondary Outcome ◽

Bayesian Hierarchical ◽

Time Reproduction ◽

Tier System ◽

The Uk ◽

National Trends ◽

Tier 3 ◽

The Impact

ObjectiveTo measure the effects of the tier system on the COVID-19 pandemic in the UK between the first and second national lockdowns, before the emergence of the B.1.1.7 variant of concern.DesignThis is a modelling study combining estimates of real-time reproduction number Rt (derived from UK case, death and serological survey data) with publicly available data on regional non-pharmaceutical interventions. We fit a Bayesian hierarchical model with latent factors using these quantities to account for broader national trends in addition to subnational effects from tiers.SettingThe UK at lower tier local authority (LTLA) level. 310 LTLAs were included in the analysis.Primary and secondary outcome measuresReduction in real-time reproduction number Rt.ResultsNationally, transmission increased between July and late September, regional differences notwithstanding. Immediately prior to the introduction of the tier system, Rt averaged 1.3 (0.9–1.6) across LTLAs, but declined to an average of 1.1 (0.86–1.42) 2 weeks later. Decline in transmission was not solely attributable to tiers. Tier 1 had negligible effects. Tiers 2 and 3, respectively, reduced transmission by 6% (5%–7%) and 23% (21%–25%). 288 LTLAs (93%) would have begun to suppress their epidemics if every LTLA had gone into tier 3 by the second national lockdown, whereas only 90 (29%) did so in reality.ConclusionsThe relatively small effect sizes found in this analysis demonstrate that interventions at least as stringent as tier 3 are required to suppress transmission, especially considering more transmissible variants, at least until effective vaccination is widespread or much greater population immunity has amassed.

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Estimating the impact of reopening schools on the reproduction number of SARS-CoV-2 in England, using weekly contact survey data

BMC Medicine ◽

10.1186/s12916-021-02107-0 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

James D. Munday ◽

Christopher I. Jarvis ◽

Amy Gimma ◽

Kerry L. M. Wong ◽

Kevin van Zandvoort ◽

...

Keyword(s):

Reproduction Number ◽

Transmission Rate ◽

Transmission Risk ◽

Individual Level ◽

Face To Face ◽

School Settings ◽

Contact Rates ◽

Contact Survey ◽

The Uk ◽

The Impact

Abstract Background Schools were closed in England on 4 January 2021 as part of increased national restrictions to curb transmission of SARS-CoV-2. The UK government reopened schools on 8 March. Although there was evidence of lower individual-level transmission risk amongst children compared to adults, the combined effects of this with increased contact rates in school settings and the resulting impact on the overall transmission rate in the population were not clear. Methods We measured social contacts of > 5000 participants weekly from March 2020, including periods when schools were both open and closed, amongst other restrictions. We combined these data with estimates of the susceptibility and infectiousness of children compared with adults to estimate the impact of reopening schools on the reproduction number. Results Our analysis indicates that reopening all schools under the same measures as previous periods that combined lockdown with face-to-face schooling would be likely to increase the reproduction number substantially. Assuming a baseline of 0.8, we estimated a likely increase to between 1.0 and 1.5 with the reopening of all schools or to between 0.9 and 1.2 reopening primary or secondary schools alone. Conclusion Our results suggest that reopening schools would likely halt the fall in cases observed between January and March 2021 and would risk a return to rising infections, but these estimates relied heavily on the latest estimates or reproduction number and the validity of the susceptibility and infectiousness profiles we used at the time of reopening.

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Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China

Science ◽

10.1126/science.abb8001 ◽

2020 ◽

Vol 368 (6498) ◽

pp. 1481-1486 ◽

Cited By ~ 202

Author(s):

Juanjuan Zhang ◽

Maria Litvinova ◽

Yuxia Liang ◽

Yan Wang ◽

Wei Wang ◽

...

Keyword(s):

Confidence Interval ◽

Odds Ratio ◽

School Closure ◽

Hunan Province ◽

Contact Tracing ◽

Transmission Model ◽

Social Distancing ◽

Susceptibility To Infection ◽

Contact Patterns ◽

The Impact

Intense nonpharmaceutical interventions were put in place in China to stop transmission of the novel coronavirus disease 2019 (COVID-19). As transmission intensifies in other countries, the interplay between age, contact patterns, social distancing, susceptibility to infection, and COVID-19 dynamics remains unclear. To answer these questions, we analyze contact survey data for Wuhan and Shanghai before and during the outbreak and contact-tracing information from Hunan province. Daily contacts were reduced seven- to eightfold during the COVID-19 social distancing period, with most interactions restricted to the household. We find that children 0 to 14 years of age are less susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than adults 15 to 64 years of age (odds ratio 0.34, 95% confidence interval 0.24 to 0.49), whereas individuals more than 65 years of age are more susceptible to infection (odds ratio 1.47, 95% confidence interval 1.12 to 1.92). Based on these data, we built a transmission model to study the impact of social distancing and school closure on transmission. We find that social distancing alone, as implemented in China during the outbreak, is sufficient to control COVID-19. Although proactive school closures cannot interrupt transmission on their own, they can reduce peak incidence by 40 to 60% and delay the epidemic.

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Intentions to “Reuse” Medication in the Future Modelled and Measured Using the Theory of Planned Behavior

Pharmacy ◽

10.3390/pharmacy8040213 ◽

2020 ◽

Vol 8 (4) ◽

pp. 213 ◽

Cited By ~ 1

Author(s):

Hamza Alhamad ◽

Parastou Donyai

Keyword(s):

Theory Of Planned Behavior ◽

Planned Behavior ◽

Educational Interventions ◽

Environmental Benefits ◽

Perceived Behavioral Control ◽

Substantial Impact ◽

Medication Waste ◽

The Future ◽

The Uk ◽

The Impact

Background: A range of pro-environmental behaviors are recognized, promoted, and investigated, but urgent action is also needed to tackle the direct and indirect environmental impact of medication waste. One solution is to reissue medicines, returned unused to pharmacies (i.e., reuse medicines). Yet, if medicines reuse is to be formally introduced in the UK, it is imperative also to understand people’s willingness to take part in such a scheme and importantly, the underpinning drivers. This study aimed to develop, validate, and evaluate a Theory of Planned Behavior model aimed at predicting medicines reuse behavioral intentions. Methods: The behavior of interest, medicines reuse, was defined according to its Target, Action, Context, and Time. Then themes from an existing qualitative study were used in order to draft, validate and pilot a Theory of Planned Behavior-based questionnaire before its completion by a representative sample (n = 1003) of participants from across the UK. Results: The majority expressed pro-medicines reuse intentions. The three direct measures accounted for 73.4% of the variance in relation to people’s intention to reuse medicines in the future, which was statistically significant at p < 0.001. People’s specific beliefs about medicines reuse and how they evaluate other people’s expectations of them had a substantial impact on their intentions to reuse medication in the future, mediated in an intricate way via attitudes, subjective norms and perceived behavioral control (PBC). Conclusions: This study shows how people could embrace medicines reuse via practical measures that illustrate the safety and quality assurance of reissued medicines, educational interventions that bolster beliefs about the pro-environmental benefits, and norm-based interventions encouraging doctors and pharmacists to endorse the practice. The findings add to the emerging work on medicines reuse and, significantly, provide a theoretical framework to guide policymakers and other organizations looking to decrease the impact of medication waste through medicines reuse schemes.

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THEORETICAL INVESTIGATION OF THE IMPACT ON EPIDEMIC THRESHOLD OF TRAVEL BETWEEN COMMUNITIES OF RESIDENT POPULATIONS

Journal of Biological System ◽

10.1142/s0218339013500101 ◽

2013 ◽

Vol 21 (02) ◽

pp. 1350010 ◽

Cited By ~ 1

Author(s):

KLOT PATANARAPEELERT ◽

D. GARCIA LOPEZ ◽

I-MING TANG ◽

MARC A. DUBOIS

Keyword(s):

Basic Reproduction Number ◽

Epidemic Model ◽

Initial Phase ◽

Reproduction Number ◽

Travel Patterns ◽

Epidemic Threshold ◽

Contact Patterns ◽

Resident Populations ◽

The Impact ◽

The Basic Reproduction Number

During the initial phase of an epidemic, individual displacements between different regions modify the contact patterns. Understanding mobility processes and their consequences is necessary to predict the subsequent spread of the disease in order to optimize control policies. The basic reproduction number is commonly used to determine the threshold between extinction and expansion of the disease. Once it is derived for an epidemic model that includes the travel of population between distinct localities, the dependence of the diseases dynamics upon travel rates becomes explicit. In this study, we examine the effects of travel on the epidemic threshold for a model of two communities. The travel rates are treated as varying subject to two scenarios. We show theoretically that if the transmission potentials within communities are moderate, the epidemic threshold can be modified by travel. The conditions for the presence of the threshold induced by travel is determined and the critical values of travel at which the basic reproduction number is equal to one are derived. We show further that these results can also be applied to a model of three communities under specific travel patterns and that the derived basic reproduction number has a form similar to that of the two communities problem.

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The effectiveness of social bubbles as part of a Covid-19 lockdown exit strategy, a modelling study

10.1101/2020.06.05.20123448 ◽

2020 ◽

Cited By ~ 1

Author(s):

Trystan Leng ◽

Connor White ◽

Joe Hilton ◽

Adam Kucharski ◽

Lorenzo Pellis ◽

...

Keyword(s):

Reproduction Number ◽

Base Case ◽

Exit Strategy ◽

Epidemic Threshold ◽

Case Scenario ◽

Base Case Scenario ◽

The Social ◽

The Uk ◽

The Impact ◽

Epidemic Risk

AbstractBackgroundDuring the Covid-19 lockdown, contact clustering in social bubbles may allow extending contacts beyond the household at minimal additional risk and hence has been considered as part of modified lockdown policy or a gradual lockdown exit strategy. We estimated the impact of such strategies on epidemic and mortality risk using the UK as a case study.MethodsWe used an individual based model for a synthetic population similar to the UK, that is stratified into transmission risks from the community, within the household and from other households in the same social bubble. The base case considers a situation where non-essential shops and schools are closed, the secondary household attack rate is 20% and the initial reproduction number is 0.8. We simulate a number of strategies including variations of social bubbles, i.e. the forming of exclusive pairs of households, for particular subsets of households (households including children and single occupancy households), as well as for all households. We test the sensitivity of the results to a range of alternative model assumptions and parameters.ResultsClustering contacts outside the household into exclusive social bubbles is an effective strategy of increasing contacts while limiting some of the associated increase in epidemic risk. In the base case scenario social bubbles reduced cases and fatalities by 17% compared to an unclustered increase of contacts. We find that if all households were to form social bubbles the reproduction number would likely increase to 1.1 and therefore beyond the epidemic threshold of one. However, strategies that allow households with young children or single occupancy households to form social bubbles only increased the reproduction number by less than 10%. The corresponding increase in morbidity and mortality is proportional to the increase in the epidemic risk but is largely focussed in older adults independently of whether these are included in the social bubbles.ConclusionsSocial bubbles can be an effective way of extending contacts beyond the household limiting the increase in epidemic risk, if managed appropriately.

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Analyses of the 1957 (Asian) influenza pandemic in the United Kingdom and the impact of school closures

Epidemiology and Infection ◽

10.1017/s0950268807008369 ◽

2007 ◽

Vol 136 (2) ◽

pp. 166-179 ◽

Cited By ~ 69

Author(s):

E. VYNNYCKY ◽

W. J. EDMUNDS

Keyword(s):

United Kingdom ◽

Reproduction Number ◽

Clinical Symptoms ◽

Influenza Pandemic ◽

School Closures ◽

Epidemic Size ◽

The United Kingdom ◽

Contact Patterns ◽

Potential Impact ◽

The Impact

SUMMARYMany countries plan to close schools during a future influenza pandemic, although the potential impact is poorly understood. We apply a model of the transmission dynamics of pandemic influenza to consultation, serological and clinical data from the United Kingdom from the 1957 (Asian) influenza pandemic, to estimate the basic reproduction number (R0), the proportion of infected individuals who experience clinical symptoms and the impact of school/nursery closures. The R0 for Asian influenza was about 1·8 and 60–65% of infected individuals were estimated to have experienced clinical symptoms. During a future pandemic, closure of schools/nurseries could reduce the epidemic size only by a very small amount (<10%) if R0 is high (e.g. 2·5 or 3·5), and modest reductions, e.g. 22% might be possible if it is low (1·8) and schools are closed early, depending on assumptions about contact patterns. Further data on contact patterns and their dependence on school closures are needed.

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Human mobility in response to COVID-19 in France, Italy and UK

Scientific Reports ◽

10.1038/s41598-021-92399-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Alessandro Galeazzi ◽

Matteo Cinelli ◽

Giovanni Bonaccorsi ◽

Francesco Pierri ◽

Ana Lucia Schmidt ◽

...

Keyword(s):

Human Mobility ◽

Substantial Reduction ◽

Value Added ◽

Economic Consequences ◽

Substantial Impact ◽

Percolation Process ◽

The Uk ◽

Network Disruption ◽

National Governments ◽

The Impact

AbstractThe COVID-19 pandemic is one of the defining events of our time. National Governments responded to the global crisis by implementing mobility restrictions to slow down the spread of the virus. To assess the impact of those policies on human mobility, we perform a massive comparative analysis on geolocalized data from 13 M Facebook users in France, Italy, and the UK. We find that lockdown generally affects national mobility efficiency and smallworldness—i.e., a substantial reduction of long-range connections in favor of local paths. The impact, however, differs among nations according to their mobility infrastructure. We find that mobility is more concentrated in France and UK and more distributed in Italy. In this paper we provide a framework to quantify the substantial impact of the mobility restrictions. We introduce a percolation model mimicking mobility network disruption and find that node persistence in the percolation process is significantly correlated with the economic and demographic characteristics of countries: areas showing higher resilience to mobility disruptions are those where Value Added per Capita and Population Density are high. Our methods and findings provide important insights to enhance preparedness for global critical events and to incorporate resilience as a relevant dimension to estimate the socio-economic consequences of mobility restriction policies.

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The population attributable fraction of cases due to gatherings and groups with relevance to COVID-19 mitigation strategies

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2020.0273 ◽

2021 ◽

Vol 376 (1829) ◽

pp. 20200273

Author(s):

Ellen Brooks-Pollock ◽

Jonathan M. Read ◽

Thomas House ◽

Graham F. Medley ◽

Matt J. Keeling ◽

...

Keyword(s):

Population Attributable Fraction ◽

Social Contact ◽

Attributable Fraction ◽

Mitigation Strategies ◽

Mass Gatherings ◽

Contact Patterns ◽

Contact Behaviour ◽

Epidemiological Impact ◽

The Uk ◽

Relative Change

Many countries have banned groups and gatherings as part of their response to the pandemic caused by the coronavirus, SARS-CoV-2. Although there are outbreak reports involving mass gatherings, the contribution to overall transmission is unknown. We used data from a survey of social contact behaviour that specifically asked about contact with groups to estimate the population attributable fraction (PAF) due to groups as the relative change in the basic reproduction number when groups are prevented. Groups of 50+ individuals accounted for 0.5% of reported contact events, and we estimate that the PAF due to groups of 50+ people is 5.4% (95% confidence interval 1.4%, 11.5%). The PAF due to groups of 20+ people is 18.9% (12.7%, 25.7%) and the PAF due to groups of 10+ is 25.2% (19.4%, 31.4%). Under normal circumstances with pre-COVID-19 contact patterns, large groups of individuals have a relatively small epidemiological impact; small- and medium-sized groups between 10 and 50 people have a larger impact on an epidemic. This article is part of the theme issue ‘Modelling that shaped the early COVID-19 pandemic response in the UK’.

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The impact of relaxing interventions on human contact patterns and SARS-CoV-2 transmission in China

Science Advances ◽

10.1126/sciadv.abe2584 ◽

2021 ◽

Vol 7 (19) ◽

pp. eabe2584

Author(s):

Juanjuan Zhang ◽

Maria Litvinova ◽

Yuxia Liang ◽

Wen Zheng ◽

Huilin Shi ◽

...

Keyword(s):

Reproduction Number ◽

School Closure ◽

School Interventions ◽

Community Activities ◽

Human Contact ◽

Contact Patterns ◽

Social Mixing ◽

The Mean ◽

Nonpharmaceutical Interventions ◽

The Impact

Nonpharmaceutical interventions to control SARS-CoV-2 spread have been implemented with different intensity, timing, and impact on transmission. As a result, post-lockdown COVID-19 dynamics are heterogeneous and difficult to interpret. We describe a set of contact surveys performed in four Chinese cities (Wuhan, Shanghai, Shenzhen, and Changsha) during the pre-pandemic, lockdown and post-lockdown periods to quantify changes in contact patterns. In the post-lockdown period, the mean number of contacts increased by 5 to 17% as compared to the lockdown period. However, it remains three to seven times lower than its pre-pandemic level sufficient to control SARS-CoV-2 transmission. We find that the impact of school interventions depends nonlinearly on the intensity of other activities. When most community activities are halted, school closure leads to a 77% decrease in the reproduction number; in contrast, when social mixing outside of schools is at pre-pandemic level, school closure leads to a 5% reduction in transmission.

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