Impact of Social Distancing in Curbing COVID-19 Pandemic: A Systematic Review

Currently, no pharmaceutical treatment or vaccine is approved for the treatment of Coronavirus. Due to these reasons, most countries turn to non-pharmaceutical approach such as social distancing. Social distancing includes strategies to ban public gatherings and advise individuals to stay at their home or maintain distance to one another by at least 1-2 meters. This study aims to intend to assess all the available evidence of social distancing in decreasing COVID-19 transmission in the general population. This study is a systematic review that was conducted an electronic search of published literature using MEDLINE/Pubmed, Science direct, PMC, Wiley, and Google Scholar and we use Joanna Briggs Institute (JBI) critical appraisal checklist to assess methodological qualities. A total of 7 articles were decided to be included in this study. Social distancing has curb down the number and saved approximately 10 thousand Brazilian lives. A study by VoPham et al on the association of social distancing and COVID-19 incidence found higher social distancing was associated with a 29% reduction of COVID-19 incidence (adjusted IRR 0.71;95% CI (0,57-0,87) and 35% reduction of COVID-19 mortality (adjusted IRR 0,65; 95% CI 0,55-0,76). Social distancing is one of the major policies implemented for long-term behavioral adjustment in managing the COVID-19 pandemic. Passive social distancing is not enough to drag down the number, there needs to be large scale testing, isolation, and contact tracing. However, we believe we have illuminated the impact of social distancing on the COVID-19 pandemic and add to the available literature the basis of social distancing in reducing transmission of COVID-19.


Introduction
Coronavirus disease 2019 (COVID-19) is a disease caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) that first emerged on December 2019 in Wuhan, China. Over the span of a few months, despite interventions from the Chinese government, the disease spreads all over the world and finally declared as a pandemic by World Health Organisation. 1 By the time of writing, 13 July 2020, Coronavirus has infected 13 millions people worldwide with more than 500 thousand fatalities. 2 Currently, no pharmaceutical treatment or vaccine is approved for the treatment of Coronavirus. Due to these reasons, World Health Organisation (WHO) recommends every country to employ aggressive tracing, case finding, isolation and quarantine of close contacts to mitigate the case numbers. 3 Social distancing is a method to minimize crowd interactions and prevent the spread of disease within groups of people. This is a common practice which has been carried out over generations, to minimize the spread of virus by limiting its reproduction rate (R0) among communities. 4 However these strategies need large resources, something most developing countries often lacked. Due to these reasons, most countries turn to non-pharmaceutical approach such as social distancing to flatten the curve. Social distancing includes strategies to ban public gatherings and advise individuals to stay at their home or mantain distance to one another by at least 1-2 meters. By reducing number of potentially infectious individual, social distancing may buy enough time for the development of more definitive treatment like vaccine and decreasing risk of overloading the healthcare system. 2,5 There are few studies on social distancing that has been published. A study carried out by Jianhong et al estimates confirm that social distancing measures have helped mitigate transmission by reducing daily infection contact rate. 5 However, to our knowledge, there hasn't been one investigating effectiveness of social distancing on COVID-19 transmission. A recently published systematic review on social distancing instead focus on investigating the optimum distance to avoid person to person transmission. 7 Another study by Koo, Cook and Park did mathematical modelling of COVID-19 transmission and found combined intervention, in which quarantine, school closure and workplace distancing implemented, was most effective compared to no intervention at all. 8 It is still uncertain whether the social distancing that has been employed has been sufficient in curbing COVID-19 number. Therefore, we intend to assess all the available evidence of social distancing in decreasing COVID-19 transmission in general population.

Protocol and registration
This study will utilise a systematic review (SR) design study. The systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement

Eligibility criteria
The inclusion criteria included studies containing how social distancing manage to impact COVID-19 pandemic. Studies must be published in English language and included cross sectional, case control and cohort design. Studies also needs to have abstract and full text available. Exclusion criteria included the following: letters, commentaries, opinion, reviews, editorial, case report and case series also qualitative studies and experimental design. Studies on social distancing that did not answer how the impact of social distancing on COVID-19 pandemic is excluded.

Selection of studies
Authors independently conducted electronic search of published literature using MEDLINE/Pubmed, Science direct, PMC, Wiley and Google Scholar. The keywords are listed in Table 1. Literature selection was performed without time limitation and restricted the searches to only published English studies. The citations will be imported to Mendeley Reference and screened twice (i) screening of titles and abstract matched with inclusion criteria and ii) review of full text. We will use the standard PRISMA flow diagram to provide the process of study selection

Quality assesment
We use Joanna Briggs Institue (JBI) critical appraisal checklist to assess methodological qualities. All included studies will be asessed by reviewers (MA & LL) using standardised questions and the results will be synthesis and interpreted.

Results and Discussion
Our search results identified 16 publications. After screening by title and abstract, a total of 8 studies matches the eligibility criteria. After reading the full text, 7 articles were decided to be included in the study. We use PRISMA flow diagram for searching and extracting data and presented on the PRISMA flow diagram ( Figure 1). Social distancing is an umbrella term encompassing several strategies, including case isolation, quarantine, school closure, distance working and contact reduction. Several studies examined the efficacy of social distancing on COVID-19 pandemic. Delen et al used the cross-national mobility trends to analyse the efficacy of social distancing and found 47% variation in COVID-19 transmission is due to change in mobility patterns from enforcing social distancing with mobility in public places such as restaurants, grocery stores, public transport being the most important determinants of transmission rate. 9 Additional records from other sources (n=28358) The study obtained the data of cumulative reported COVID-19 infected cases in Ontario, Canada, from the Government of Canada. The data were released and analyzed anonymously.
The study conclude social distancing measures have helped mitigate ransmission by reducing daily infection contact rate, but the disease transmission probability per contact remains as high as 0.145 and case detection rate was so low that the effective reproduction number remained higher than the threshold for disease control until the closure of non-essential business in the Province. Delen et al 9 The indicating a gradually efficacy of interventions adopted. 6 The study also predicted the number of cumulative confirmed cases per 7 April to be 6132 (95% CI 4250-8000) and could be reduced further by decreasing contact rates further by 90%. Study by VoPham et al on association of social distancing and COVID-19 incidence found higher social distancing was associated with 29% reduction of COVID-19 incidence (adjusterd IRR 0.71;95% CI (0,57-0,87) and 35% reduction of COVID-19 mortality (adjusted IRR 0,65; 95% CI 0,55-0,76). 11 Contrary to the previous studies, Martin Calvo found social distancing strategies doesn't effectively controlled the epidemic as infection can still occur somewhere else, for example in household. 12 Therefore, passive social distancing is not enough to drag down the number, there needs to be large scale testing, isolation and contact tracing. Tran Phuoc Bao found social distancing has worked on 10 countries although the effect showed after 1-4 weeks. 13 Courthemanche argued without social distancing being issued, there would be 10 times greater the number of COVID-19 infection and more than 35 times spread. 14 COVID-19 arguably has changed the way the world works. Social distancing is one of the major policies implemented for long-term behavioural adjustment in managing COVID-19 pandemic. Due to the risk carried by the virus, every individual of a community needs to protect the vulnerable groups such as comorbid group, homeless, etc to decrease transmission of COVID-19.
Social distancing is the method to minimize crowd interaction and therefore decrease the spread of a disease within people. 15 COVID-19 outbreak isn't the first time social distancing has been implemented. Previous occurrence includes 1918 influenza pandemic in which, 50-100 million deaths were reported worldwide. Although official social distancing order hadn't been issued, the crowd initiate social distancing on their own that made it possible to decrease mortality of the outbreak. 16 The potential limitation of our systematic review is majorities of the studies assessing effectiveness of social distancing is done via simulations and use estimated parameters to predict the number of cases averted after the implementation. This should be interpreted with caution as the number is subject to high level of uncertainty that's difficult to quantify. Another possible limitation would be some studies had small sample size which may impact generalization.

Conclusion
In conclusion, social distancing is one of the major policies implemented for long-term behavioural adjustment in managing COVID-19 pandemic. Passive social distancing is not enough to drag down the number, there needs to be large scale testing, isolation and contact tracing. However, we believe we have illuminated the impact of social distancing on COVID-19 pandemic and add to the available literature the basis of social distancing in reducing transmission of COVID-19.