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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Suggested Citation:"Rapid Expert Consultation." National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020). Washington, DC: The National Academies Press. doi: 10.17226/25753.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

March 19, 2020 Kelvin Droegemeier, Ph.D. Office of Science and Technology Policy Executive Office of the President Eisenhower Executive Office Building 1650 Pennsylvania Avenue Washington, DC 20504 Dear Dr. Droegemeier: This letter responds to your question about evidence on the effectiveness and costs of social distancing measures in contending with COVID-19. Respiratory viruses are transmitted from person to person via air droplet (talk, sneeze, cough), suspended droplet nuclei (<5 microns diameter; sneeze, cough) and surface fomites (touch contaminated surface and then touch mucous membrane in eye, nose, mouth). Social distancing measures are based on the idea of interrupting these forms of transmission by separating infected and uninfected persons. In the absence of a vaccine or effective prophylactic agents, social distancing is the principal tool available to blunt the force of an epidemic (Qualls, et al. 2017). The attached summaries and table of selected references were prepared by staff of the National Academies of Sciences, Engineering, and Medicine based on input from Alexandra Phelan and me. Ned Calonge, The Colorado Trust, Sue Curry, University of Iowa, and Steven Teutsch, University of California, Los Angeles, reviewed this document, and Ellen Clayton, Vanderbilt University, approved the document on behalf of the Report Review Committee. The attached materials summarize evidence bearing on the effectiveness of social distancing measures, and they demonstrate that social distancing measures are effective. However, their effectiveness depends on such factors as early implementation and compliance. Most of these studies are based on experience with influenza. Some are empirical studies of the experience in different places that employed varying degrees of social separation during the great influenza pandemic of 1918-1919. Others are modeling exercises using available data and certain assumptions about relevant characteristics of an infection, such as the basic reproductive number, degree of mixing, and fraction of susceptible individuals. In general, these studies support the value of social distancing in reducing the amount of illness and death and in spreading onset of illness over a longer time period (“flattening the curve”), which makes clinical management more feasible. For example, one study of 34 U.S. cities during the 1918-1919 influenza pandemic found that those communities that implemented social distancing measures earlier experienced greater delays in reaching peak mortality, lower peak mortality rates, and lower total mortality (Markel, et al. 2007). 500 Fifth Street, NW, Washington, DC 20001

In interpreting these data, it is important to note that “social distancing” can cover a wide range of community-based interventions, from closing schools and workplaces to eliminating mass public events, to wearing face masks, and it is not always clear exactly which intervention is contributing what degree to the differential outcomes. Also important in the current context are differences between influenza and SARS-CoV-2 in such key attributes as transmission rate, incubation period, uncertainty regarding children as vectors, and pre-existing immunity in the population. In general, studies based on historical data and on modeling both indicate that social distancing interventions are more effective when instituted early in the course of an epidemic (Hatchet et al., 2007; Halloran et al., 2008). Only a handful of studies consider cost-effectiveness of this class of interventions, and many of them include consideration of pharmaceutical interventions such as antiviral treatments and vaccination strategies which are not currently available for this pandemic (Milne, 2013; Pasquine, 2017; Velasco, 2012; Pelroth, 2009). In general, these studies do not fully incorporate all social and economic costs that attend to such interventions as cancellation of travel and suspension of many businesses. They are not updated to today’s economic and social circumstances, and the comparison to “benefits” relate to the burden of influenza, not SARS-CoV-2. Therefore, they do not have much to reveal about the cost or cost-effectiveness of today’s interventions in the current pandemic. More pertinent to decision making today about COVID-19 is the experience of other countries where the pandemic preceded outbreaks in the United States. In an informative analysis, for example, Wang et al. (2020) evaluated the impact of social distancing and case finding and isolation of patients over three phases of the epidemic in Wuhan, China. Prior to introducing any of these measures, the basic reproductive number was estimated to be 3.86 (95% credible interval 3.74 to 3.97) This period, from December 8, 2019 to January 23, 2020 was marked by an exponential growth in new cases. From January 23, 2020 to February 2, 2020, the following social distancing measures were implemented: home quarantine for suspected cases, cordon sanitaire, suspension of public transportation, closure of entertainment venues and public spaces, compulsory wearing of facemasks, mandated personal hygiene, and body temperature self-monitoring. During this period, the reproductive number fell to 1.26, a substantial improvement, but still above the level of 1.0 that sustains spread. From February 2, 2020 and on, cordon sanitaire, suspension of public transportation, closure of entertainment venues and public spaces continued, and the following measures were also implemented: centralized isolation in designated hospitals for cases; mobile-cabin hospitals, schools, and hotels for exposed and possible cases; universal and strict stay-at-home policy for all residents unless permitted; widespread temperature and symptom monitoring; universal screening and reporting. With these added measures the basic reproductive number fell to 0.32, and the epidemic subsided. The interventions were estimated to prevent 94.5% (93.7 to 95.2%) of infections until February 18. A recent modeling exercise reported from Imperial College London (Ferguson, et al. 2020) examined the effectiveness of different social distancing strategies to mitigate or suppress

the force of the epidemic in the U.K. and the U.S. The overall conclusion is that population-wide social distancing in combination with home isolation of cases, quarantine of exposed individuals, and school and university closure could reduce the incidence of new cases (suppress) and not merely slow the rise (mitigate). However, to avoid re- emergence of disease, their models indicate these interventions would need to be maintained until an effective vaccine were developed and deployed, and this could take 18 months or longer. The authors stress uncertainty in estimates of transmissibility and effectiveness of interventions. They acknowledge the practical possibility of shorter-term interventions and variation across geographies depending on the local stage of the outbreak. Their analysis suggests that a three-month period of intervention, stressing social distancing of vulnerable (older or chronically ill) populations in combination with other measures could reduce deaths in half and peak healthcare demand by two thirds. At the same time, half-measures, such as case isolation and social distancing of the elderly only (rather than the entire population), could lead to an epidemic that overwhelms hospital surge capacity and, they project, could cause more than a million deaths in the U.S. Anecdotally, Singapore, which after the experience of the SARS outbreak in 2002 refined its capacity for intensive detection, isolation of cases, contact tracing, and quarantine of exposed individuals, has managed to suppress the SARS-CoV-2 epidemic without resorting as yet to closing schools and workplaces. These results are possible only with the availability of widespread diagnostic testing. The continued influx of new cases, probably related to travel, creates an ongoing challenge for the public health authorities there. In the U.S., we are embarked on a natural experiment where different communities will likely enact different levels and timing of social distancing relative to the local phase of the epidemic. Experience in other countries during the current COVID-19 pandemic shows the value of widely-available diagnostic testing to guide the response. If our nation mounts a coordinated effort to detect and monitor disease incidence and tracks the control measures that are being implemented in each community, compliance rates, and other relevant data, we can better inform decisions about when social distancing measures may be withdrawn and in what circumstances they may need to be reinstated or enlarged. Judgments about when to suspend which social distancing measures will be critical and should involve discussions with public health experts, mathematical modelers, economists, and social and behavioral scientists. Decision makers will be greatly aided by ongoing data collection and disease monitoring. My colleagues and I hope this rapid expert consultation is helpful to you as you continue to guide the nation’s response in this ongoing public health crisis. Respectfully, Harvey V. Fineberg, M.D., Ph.D. Chair Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats

Summary of Articles Examining the Effectiveness of Social Distancing Access to Full-Text Articles Please note that a brief glossary is included at the end of this document Workplace Social Distancing • Ahmed and colleagues (2018) conducted a systematic review of the evidence of effect on social distancing in non-healthcare workplaces (e.g., telecommute policies) to reduce or slow the transmission of influenza. This review found that social distancing in non-healthcare workplaces settings was associated with a reduction in ILI and seroconversion to H1N1, and delayed and reduced the peak attack rate. Effectiveness declined with higher basic reproduction number values, delayed triggering of social distancing, or lower compliance. Important to note that these findings were primarily supported by modeling studies. School Closures • CDC’s Community Preventive Services Task Force, and evidence-based guidelines group, conducted a systematic review in 2012 of school dismissals to reduce transmission of pandemic influenza. The Task Force recommended pre-emptive, coordinated school dismissals during a severe influenza pandemic (a pandemic with high rates of severe illness such as that experienced in 1918) based on sufficient evidence of effectiveness in reducing or delaying the spread of infection and illness within communities. This recommendation was based on findings of assessments of measures taken during the 1918 pandemic and modeling studies that indicated that benefits of timely, coordinated, and sustained dismissals outweigh the expected societal and economic costs. It is important to note that there were different societal and cultural issues in 1918, including the fact that there were fewer two-working-parent families, which could affect the benefits and costs of school closures then compared to today. Travel Restrictions • Chinazzi and colleagues (2020) applied a transmission model to project the impact of travel limitations on the national and international spread of COVID-19. The travel quarantine of Wuhan delayed the overall epidemic progression by only 3 to 5 days in Mainland China, but had a more marked effect at the international scale, where case importations were reduced by nearly 80% until mid-February. The modeling study shows that additional travel limitations up to 90% of the traffic have a modest effect unless paired with public health interventions and behavioral changes that achieve a considerable reduction in the disease transmissibility. Moving forward the authors expect that travel restrictions to COVID-19 affected areas will have modest effects, and that other transmission-reduction interventions will provide the greatest benefit to mitigate the epidemic.

• A systematic review examined the effectiveness of internal and international travel restrictions in the rapid containment of influenza (Mateus et al., 2014). This review found across 23 included studies that internal travel restrictions and international border restrictions delayed the spread of influenza epidemics by one week and two months, respectively. International travel restrictions delayed the spread and peak of epidemics by periods varying between a few days and four months. Travel restrictions reduced the incidence of new cases by less than 3%. Impact was reduced when restrictions were implemented more than six weeks after the notification of epidemics or when the level of transmissibility was high. Use of Multiple Non-Pharmaceutical Interventions (Note many of these are modeling studies) • One of the most recent examinations of social distancing measures, Ferguson and colleagues (2020) applied a simulation model to assess the role of non-pharmaceutical interventions aimed at reducing transmission of SARS-CoV-2 in the U.K. and U.S. This study found that optimal mitigation (i.e., slowing the epidemic curve) policies (combining home isolation of suspect cases, home quarantine of those living in the same household as suspect cases, and social distancing of the elderly and others at most risk of severe disease) might reduce peak healthcare demand by 2/3 and deaths by half. Reversing the epidemic growth (i.e., suppression) will require at a minimum a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members. The major challenge of suppression is that this type of intensive intervention package – or something equivalently effective at reducing transmission – will need to be maintained until a vaccine becomes available. • Lee et al., (2020) authored a case study on Singapore’s approach on containment efforts to interrupting the transmission of COVID-19. Despite early importations resulting in local chains of transmission, the rise in the number of cases has been steady without the exponential growth observed elsewhere. This was in part due to Singapore’s strategy of using a comprehensive surveillance system to detect as many cases as possible, and to contain them at the individual level. This suggests that this strategy, coupled with community-based measures proportionate to the transmission risk, has been effective in containing spread, and could be considered in countries in the early stages of the outbreak where it is not possible to mount massive community-wide containment efforts. • Wang et al. (2020) evaluated the impact of non-pharmaceutical interventions on the epidemic in Wuhan, China. The effective reproductive number dropped from 3.86 (95% credible interval 3.74 to 3.97) before interventions to 0.32 (0.28 to 0.37) post interventions. Specifically, from December 8, 2019 – January 23, 2020 there was unabated spread and no social distancing measures (R t of 3.86). From January 23, 2020 – February 2, 2020, the following social distancing measures were implemented: home quarantine for suspected cases, cordon sanitaire, public transportations suspension, closure of entertainment venues and public spaces, compulsory wearing facemasks, personal hygiene, and body temperature self-monitoring (R t of 1.26). From February 2, 2020 and on, cordon sanitaire, public transportations suspension, closure of entertainment venues and public spaces remained but the following measures were also implemented: centralized isolation in designated hospitals, mobile-cabin hospitals, schools, and hotels, universal and strict stay-at-home policy for all residents unless permitted, universal

temperature and symptom monitoring, universal screening and reporting (R t of 0.32). The interventions were estimated to prevent 94.5% (93.7 to 95.2%) infections until February 18. • Yang et al. (2011) modeled the effectiveness of different non-pharmaceutical interventions used to control an influenza epidemic in a city. Control measures included social distancing, school closure, and household quarantine. Simulated results showed that household quarantine was the most effective control measure, while school closure and household quarantine implemented together achieved the greatest benefit. Household quarantine resulted in a decrease in the peak number of cases from more than 300 to around 158 for a 100% compliance level, a decrease of about 48.7%. The delay in the outbreak peak was about 3 to 17 days. The total number of cases decreased to a range of 3635-5403 (63.7%-94.7% of the baseline value). Earlier implementation of control measures leads to greater efficacy. Refraining from social activities with various compliance levels was relatively ineffective. • Perlroth et al. (2010) modeled the health outcomes and costs for 4 social distancing strategies and 2 antiviral medication strategies used to mitigate the impacts of an influenza pandemic in the U.S. For a pandemic strain with 1% mortality, Ro > 2.1 and assuming 60% population compliance, the preferred strategy utilized a combination of adult and child social distancing, school closure, and antiviral treatment and prophylaxis. This strategy reduced the prevalence of cases from 35% to 10%, averted 2480 cases per 10,000 population, cost $2700 per case averted and $31,300 per quality-adjusted life-year gained, as compared to a strategy without school closure. Adding school closure to adult and child social distancing and antiviral treatment/prophylaxis was not cost-effective for viral strains with Ro ≤ 1.6 and a case fatality rate < 1%. High population compliance lowered costs to society substantially when Ro > 2.1. • Uribe-Sanchez et al. (2010) describe a decision-aid methodology for developing dynamic predictive mitigation strategies for a network of regional pandemic outbreaks. A large-scale simulation-based dynamic optimization model was used to generate mitigation strategies for an efficient, progressive allocation of limited resources, including stockpiles of vaccines and antiviral drugs, healthcare capacities for administration of vaccination and antiviral therapy, and social distancing enforcement resources. Sensitivity analysis was used to estimate the marginal impact of changes in the total budget availability and variability of some critical factors, including vaccine and antiviral efficacy, and social distancing declaration threshold, duration, and target population conformance. The authors also analyze the effect of social distancing policies on the dynamics of societal and economic costs for low (Ro =1.5) and high transmissibility scenarios (Ro = 2.5). The analysis showed that the overall pandemic cost was significantly affected by the social distancing conformance, particularly in high transmissibility scenarios. Later implementation of social distancing lead to increased numbers of infections and fatalities. For both transmissibility scenarios, longer social distancing period (starting from 10 and up to 14 total days) had a significant impact on the pandemic cost by reducing both the contact intensity within the mixing groups and the size of the post-quarantine infectious population. • Davey et al. (2008a) modeled the thresholds for rescinding two community mitigation strategies (child sequestering or all-community sequestering) after an influenza pandemic. They examined rescinding child sequestering or all-community sequestering when illness during an influenza pandemic waned to thresholds of 0, 1, 2, or 3 newly identified cases (within a simulated community of 10,000) in 7 days in a mild or severe pandemic. They sought a balance of the

effect of illness, risk of epidemic reoccurrence, and minimization of the duration of mitigation strategies. When modeled with the highest compliance (90%) and reinstitution of strategies in the event of epidemic recurrence, a rescinding threshold of 0 cases applied as a component of community sequestering contained mild or severe epidemics with fewest days of mitigation strategy needed. Peak illness rates did not exceed 1% of the population and infection rates were <10%. When less conservative rescinding thresholds of 1, 2, or 3 cases were used (strategies applied with high compliance), epidemic recurrences required multiple reinstitution of cycles, ultimately yielding marked increases in cases, number of adult days at home, and epidemic duration. Reinstitution of strategies in the event of epidemic recurrence was necessary to prevent near base case levels of illness. Such reinstitution will be a critical action in an epidemic resurgence or in the event of a multiwave pandemic. Of note, for severe epidemics, high compliance was a necessary condition for successful mitigation strategies; a more restrictive rescinding threshold did not compensate for low compliance. • Davey et al. (2008b) modeled the effects of various community mitigation strategies for pandemic influenza. For a 1918-like pandemic, the best strategy minimizes illness to <1% of the population and combines network-based (e.g. school closure, social distancing of all with adults’ contacts at work reduced), and case-based measures (e.g. antiviral treatment of the ill and prophylaxis of household members). This strategy was robust to removal of enhanced transmission by the young, additional complexity in contact networks, and altered influenza natural history including extended viral shedding. In order of impact, mitigation success depended on rapid strategy implementation, high compliance, regional implementation of mitigation strategies, and stringent rescinding criteria. • Halloran et al. (2008) describe three models used to examine the effect of a targeted layered strategy for containment of pandemic influenza in the U.S. The models focused on a population size similar to that of Chicago (~8.6 million) and interventions included treatment and isolation of ascertained cases, antiviral prophylaxis and quarantine of household contacts, school closure, workplace social distancing (e.g., telework, staggered work hours), and community social distancing (e.g., closure of social venues, canceling mass gatherings). The simulations suggested that at the expected transmissibility of a pandemic strain (Ro ranging from 1.9-3.0), timely implementation of a combination of targeted household antiviral prophylaxis, and social distancing measures could substantially lower the illness attack rate before a highly efficacious vaccine could become available. Interventions were notably less effective when not initiated until a cumulative illness attack rate of 10% was reached. In all three models, most of the reduction in the attack rates appeared to come from the non-pharmaceutical interventions (versus antiviral treatment and household prophylaxis) and school closures played an important role. • Hatchett and colleagues (2007) obtained data on the timing of 19 classes of non-pharmaceutical interventions in 17 U.S. cities during the 1918 pandemic and tested the hypothesis that early implementation of multiple interventions was associated with reduced disease transmission. Consistent with this hypothesis, cities in which multiple interventions were implemented at an early phase of the epidemic had peak death rates approximately 50% lower than those that did not and had less-steep epidemic curves. Cities in which multiple interventions were implemented at an early phase of the epidemic also showed a trend toward lower cumulative excess mortality, but the difference was smaller (approximately 20%) and less statistically

significant than that for peak death rates. This finding was not unexpected, given that few cities maintained non-pharmaceutical interventions longer than 6 weeks in 1918. Early implementation of certain interventions, including closure of schools, churches, and theaters, was associated with lower peak death rates, but no single intervention showed an association with improved aggregate outcomes for the 1918 phase of the pandemic. • Markel et al. (2007) examined the implementation of non-pharmaceutical interventions in 43 cities during the 1918 pandemic and found that school closure and public gathering bans activated concurrently represented the most common combination implemented in 34 cities (79%); this combination had a median duration of 4 weeks (range, 1-10 weeks) and was significantly associated with reductions in weekly excess death rate. The cities that implemented non-pharmaceutical interventions earlier had greater delays in reaching peak mortality, lower peak mortality rates, and lower total mortality. There was a statistically significant association between increased duration of non-pharmaceutical interventions and a reduced total mortality burden. • Ferguson and colleagues (2006) applied a mathematical model to assess strategies for mitigating an influenza pandemic. This study found that border restrictions and/or internal travel restrictions are unlikely to delay spread by more than 2–3 weeks, unless more than 99% effective. School closure during the peak of a pandemic can reduce peak attack rates by up to 40%, but has little impact on overall attack rates, whereas case isolation or household quarantine could have a significant impact, if feasible. • Carrat et al. (2006) modeled the effects of different interventions aimed at preventing and controlling an influenza pandemic in a simulated community of 10,000. Interventions evaluated included vaccination, treatment/prophylaxis with neuraminidase inhibitors, quarantine, and closure of schools or workplaces. Specific to social distancing measures, the authors report that closing schools when the number of infections in the community exceeded 5 per 1000 community members (and not reopening until 10 days after the last observed case of infection) would be very effective, limiting the size of outbreaks to 10% of the population (range 0.9%– 22%). When workplaces and schools were closed (but for a shorter time than schools alone), infections were limited to 1% of the population (range 0.6-2.1) but resulted in substantially higher lost workdays. • CDC also published Community Mitigation Guidelines to Prevent Pandemic Influenza (Qualls, et al., 2017) that may be useful to reference in the current outbreak. Cost and Economic Analyses (Note many of these examined strategies in cost per life year saved, and examined non-pharmaceutical interventions as well as pharmaceutical interventions) • Pasquini-Descomps and colleagues (2017) conducted a systematic review of articles that provide cost-effectiveness or cost-benefit analysis for H1N1 pandemic interventions. Findings from the 18 included articles suggest that hospital quarantine, vaccination, and usage of the antiviral stockpile are highly cost-effective, even for mild pandemics. School closures, antiviral treatments, and social distancing may not qualify as efficient measures, for a virus like 2009's H1N1 and a willingness-to-pay threshold of $45,000 per disability-adjusted life-year. However, such interventions may become cost-effective for severe crises.

• Milne and colleagues (2013) conducted a cost effective analysis of a comprehensive range of social distancing and antiviral drug strategies intended to mitigate a future pandemic in Australia. Intervention strategies combining school closure with antiviral treatment and prophylaxis are the most cost effective strategies in terms of cost per life year saved (LYS) for all severity categories. The cost component in the cost per LYS ratio varies depending on pandemic severity: for a severe pandemic (CFR of 2.5%) the cost is $9 k per LYS. With high severity pandemics (CFR .0.75%) the most effective attack rate reduction strategies are also the most cost effective. • A systematic review by Velasco et al., 2012, examined published and unpublished evaluations of preparedness strategies and interventions against pandemic influenza. Pharmaceutical plus non- pharmaceutical interventions are relatively cost effective in comparison to vaccines and/or antivirals alone. Pharmaceutical interventions vary from cost saving to high cost effectiveness ratios. According to ceiling thresholds (Gross National Income per capita), the reduction of nonessential contacts and the use of pharmaceutical prophylaxis plus the closure of schools are amongst the cost effective strategies for all countries. However, quarantine for household contacts is not cost effective even for low- and middle-income countries.

Table 1. Summary of Articles Title Authors Year Journal Infectious Methods High-Level Results Disease Workplace Social Distancing Effectiveness of Ahmed 2018 BMC Influenza Systematic review of • Social distancing in non-healthcare workplaces workplace social et al. Public the evidence of effect settings was associated with a reduction in ILI distancing measures in Health on social distancing in and seroconversion to H1N1, and delayed and reducing influenza non-healthcare reduced the peak attack rate transmission: a workplaces (e.g., • Effectiveness declined with higher basic systematic review telecommute policies) reproduction number values, delayed triggering to reduce or slow the of social distancing, or lower compliance. transmission of • Important to note that these findings were influenza primarily supported by modeling studies. School Closures Emergency preparedness CDC – 2012 N/A Influenza CDC’s Community • The Task Force recommended pre-emptive, and response: School Commun (Pandemic) Preventive Services coordinated school dismissals during a severe dismissals to reduce ity Task Force, and influenza pandemic (a pandemic with high rates transmission of pandemic Preventiv evidence-based of severe illness such as that experienced in influenza e guidelines group, 1918) based on sufficient evidence of Services conducted a effectiveness in reducing or delaying the spread Task systematic review in of infection and illness within communities. Force 2012 of school • This recommendation was based on findings of dismissals to reduce assessments of measures taken during the 1918 transmission of pandemic and modeling studies that indicated pandemic influenza that benefits of timely, coordinated, and sustained dismissals outweigh the expected societal and economic costs.

Title Authors Year Journal Infectious Methods High-Level Results Disease Use of Multiple NPIs Impact of non- Ferguson 2020 N/A COVID-19 Epidemiological • Two fundamental strategies are possible: (a) pharmaceutical et al. (MRC) modelling of NPIs mitigation, which focuses on slowing but not interventions (NPIs) to (microsimulation necessarily stopping epidemic spread – reduce COVID19 model to two reducing peak healthcare demand while mortality and healthcare countries: UK & US) protecting those most at risk of severe disease demand from infection, and (b) suppression, which aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely. • Mitigation would still likely result in hundreds of thousands of deaths and health systems being overwhelmed; this leaves suppression as the preferred policy option. • suppression will minimally require a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members. This may need to be supplemented by school and university closures. • It remains to be seen whether long term suppression is possible, and whether the social and economic costs of the interventions adopted thus far can be reduced

Title Authors Year Journal Infectious Methods High-Level Results Disease Interrupting transmission Lee et al. 2020 N/A (pre- COVID-19 Observational review / • Despite multiple importations resulting in local of COVID-19: lessons print) lessons learned from chains of transmission, Singapore has been able from containment efforts Singapore to control the COVID-19 outbreak without in Singapore major disruption to daily living. • Strategy of using a comprehensive surveillance system to detect as many cases as possible, and to contain them at the individual level • This strategy, coupled with community-based measures proportionate to the transmission risk, has been effective in containing spread, and could be considered in countries in the early stages of the outbreak where it is not possible to mount massive community-wide containment efforts.

Title Authors Year Journal Infectious Methods High-Level Results Disease Evolving epidemiology Wang et 2020 N/A (pre- COVID-19 Epidemiological case • From December 8, 2019 – January 23, 2020 and impact of non- al. print) study from Wuhan, there was unabated spread and no social pharmaceutical China distancing measures (R t of 3.86). interventions on the • From January 23, 2020 – February 2, 2020, the outbreak of Coronavirus following social distancing measures were disease 2019 in Wuhan, implemented: home quarantine for suspected China cases, cordon sanitaire, public transportations suspension, closure of entertainment venues and public spaces, compulsory wearing facemasks, personal hygiene, and body temperature self-monitoring (R t of 1.26). • From February 2, 2020 and on, cordon sanitaire, public transportations suspension, closure of entertainment venues and public spaces remained but the following measures were also implemented: centralized isolation in designated hospitals, mobile-cabin hospitals, schools, and hotels, universal and strict stay-at- home policy for all residents unless permitted, universal temperature and symptom monitoring, universal screening and reporting (R t of 0.32). • The interventions were estimated to prevent 94.5% (93.7 to 95.2%) infections until February 18.

Title Authors Year Journal Infectious Methods High-Level Results Disease Analysis of CDC social Yang et 2011 BMC Influenza Epidemiological • Simulated results showed that household control measures using al. Infectious (Pandemic) Modeling (Individual quarantine was the most effective control an agent-based Diseases Space-Time Activity- measure, while school closure and household simulation of an influenza based Model) to quarantine implemented together achieved the epidemic in a city simulate the greatest benefit. effectiveness of non- • Household quarantine resulted in a decrease in pharmaceutical the peak number of cases from more than 300 control measures to around 158 for a 100% compliance level, a including: (1) decrease of about 48.7%. The delay in the refraining from social outbreak peak was about 3 to 17 days. activities, (2) school • The total number of cases decreased to a range closure and (3) of 3635-5403 (63.7%-94.7% of the baseline household quarantine, value). Earlier implementation of control for a hypothetical measures leads to greater efficacy. influenza outbreak in • Refraining from social activities with various an urban area. compliance levels was relatively ineffective. A Predictive decision aid Uribe- 2010 OR Influenza Large-scale • Overall pandemic cost was significantly affected methodology for dynamic Sanchez Spectrum (Pandemic) simulation-based by the social distancing conformance, mitigation of influenza et al. optimization particularly in high transmissibility scenarios. pandemics methodology for • Later implementation of social distancing lead developing dynamic to increased numbers of infections and predictive mitigation fatalities. strategies for a • For both transmissibility scenarios, longer social network of regional distancing period (starting from 10 and up to 14 pandemic outbreaks. total days) had a significant impact on the The methodology pandemic cost by reducing both the contact considers measures of intensity within the mixing groups and the size morbidity, mortality, of the post-quarantine infectious population. and social distancing, translated into the societal and economic costs of lost productivity and medical expense.

Title Authors Year Journal Infectious Methods High-Level Results Disease Combination strategies Lee et al. 2009 BMC Influenza Review of 19 modeling • Two studies suggested a high probability of for pandemic influenza Medicine (Pandemic) publications successful influenza epicenter containment response - a systematic quantifying the with combination strategies under favorable review of mathematical effectiveness of conditions. modeling studies combination • Combination strategies delayed spread, strategies (PI and NPI) reduced overall number of cases, and delayed and reduced peak attack rate more than individual strategies. • Combination strategies remained effective at high reproductive numbers compared with single strategy. • Global cooperative strategies, including redistribution of antiviral drugs, were effective in reducing the global impact and attack rates of pandemic influenza. • Combination strategies increase the effectiveness of individual strategies. Health outcomes and Pelroth 2009 Clinical Influenza Development of • For a pandemic strain with 1% mortality, Ro > costs of community et al. Infectious (Pandemic) model of influenza 2.1 and assuming 60% population compliance, mitigation strategies for Diseases severity, health care the preferred strategy utilized a combination of an influenza pandemic in (Oxford utilization, and costs adult and child social distancing, school closure, the United States Journals) to use in conjunction and antiviral treatment and prophylaxis. This with results from an strategy reduced the prevalence of cases from agent-based, social 35% to 10%, averted 2480 cases per 10,000 contact network population, cost $2700 per case averted and model developed by $31,300 per quality-adjusted life-year gained, as Sandia National compared to a strategy without school closure. Laboratories • Adding school closure to adult and child social (published previously distancing and antiviral treatment/prophylaxis by Davey and Glass) was not cost-effective for viral strains with Ro ≤ 1.6 and a case fatality rate < 1%. High population compliance lowered costs to society substantially when Ro > 2.1.

Title Authors Year Journal Infectious Methods High-Level Results Disease Rescinding community Davey 2008a Emerging Influenza Network, agent-based • When modeled with the highest compliance mitigation strategies in an and Infectious (Pandemic) computational model and reinstitution of strategies in the event of influenza pandemic Glass Diseases epidemic recurrence, a rescinding threshold of 0 cases applied as a component of community sequestering contained mild or severe epidemics with fewest days of mitigation strategy needed. • Peak illness rates did not exceed 1% of the population and infection rates were <10%. When less conservative rescinding thresholds of 1, 2, or 3 cases were used (strategies applied with high compliance), epidemic recurrences required multiple reinstitution of cycles, ultimately yielding marked increases in cases, number of adult days at home, and epidemic duration. • Reinstitution of strategies in the event of epidemic recurrence was necessary to prevent near base case levels of illness. Such reinstitution will be a critical action in an epidemic resurgence or in the event of a multiwave pandemic. Effective, robust design of Davey et 2008b PLoS ONE Influenza Epidemiological • For a 1918-like pandemic, the best strategy community mitigation for al. (Pandemic) modeling of a broad minimizes illness to <1% of the population and pandemic influenza: A range of influenza combines network-based (e.g. school closure, systematic examination pandemic scenarios social distancing of all with adults’ contacts at of proposed U.S. and mitigation work reduced), and case-based measures (e.g. guidance strategies using a antiviral treatment of the ill and prophylaxis of networked, agent- household members). based model of a community of explicit, multiply-overlapping social contact network.

Title Authors Year Journal Infectious Methods High-Level Results Disease Modeling targeted Hallloran 2008 PNAS Influenza Epidemiological • The simulations suggested that at the expected layered containment of et al. (Pandemic) Modeling (individual- transmissibility of a pandemic strain (Ro ranging an influenza pandemic in based, stochastic from 1.9-3.0), timely implementation of a the United States simulation models) to combination of targeted household antiviral examine the prophylaxis, and social distancing measures consequences of could substantially lower the illness attack rate intervention strategies before a highly efficacious vaccine could chosen in consultation become available. with U.S. public health • Interventions were notably less effective when workers not initiated until a cumulative illness attack rate of 10% was reached. • In all three models, most of the reduction in the attack rates appeared to come from the non- pharmaceutical interventions (versus antiviral treatment and household prophylaxis) and school closures played an important role.

Title Authors Year Journal Infectious Methods High-Level Results Disease Public health Hatchet 2007 PNAS Influenza Retrospective data • Cities in which multiple interventions were interventions and et al. (1918 analysis 19 classes of implemented at an early phase of the epidemic epidemic intensity during Pandemic) NPIs in 17 U.S. cities had peak death rates approx. 50% lower than the 1918 influenza during the 1918 those that did not and had less-steep epidemic pandemic pandemic curves. • Cities in which multiple interventions were implemented at an early phase of the epidemic also showed a trend toward lower cumulative excess mortality, but the difference was smaller (approx. 20%) and less statistically significant than that for peak death rates • This finding was not unexpected, given that few cities maintained NPIs longer than 6 weeks in 1918. • Early implementation of certain interventions, including closure of schools, churches, and theaters, was associated with lower peak death rates, but no single intervention showed an association with improved aggregate outcomes for the 1918 phase of the pandemic. • These findings support the hypothesis that rapid implementation of multiple NPIs can significantly reduce influenza transmission, but that viral spread will be renewed upon relaxation of such measures.

Title Authors Year Journal Infectious Methods High-Level Results Disease Non-pharmaceutical Markel 2007 JAMA Influenza Historical archival • School closure and public gathering bans Interventions et al. (1918 research, and activated concurrently represented the most Implemented by U.S. Pandemic) statistical and common combination implemented in 34 cities cities during the 1918- epidemiological (79%); this combination had a median duration 1919 influenza pandemic Analyses of 4 weeks (range, 1-10 weeks) and was significantly associated with reductions in weekly excess death rate. • The cities that implemented non- pharmaceutical interventions earlier had greater delays in reaching peak mortality (Spearman r=−0.74, P<.001), lower peak mortality rates (Spearman r=0.31, P=.02), and lower total mortality (Spearman r=0.37, P=.008). • There was a statistically significant association between increased duration of non- pharmaceutical interventions and a reduced total mortality burden (Spearman r=−0.39, P=.005).

Title Authors Year Journal Infectious Methods High-Level Results Disease Strategies for mitigating Ferguson 2006 Nature Influenza Epidemiological • Border restrictions and/or internal travel an influenza pandemic et al. (Pandemic) modelling of mixed restrictions are unlikely to delay spread by intervention options more than 2–3weeks unless more than 99% should initial effective. containment of a • School closure during the peak of a pandemic novel influenza can reduce peak attack rates by up to 40%, but outbreak fail, using US has little impact on overall attack rates, and UK as examples whereas case isolation or household quarantine could have a significant impact, if feasible. • Treatment of clinical cases can reduce transmission, but only if antivirals are given within a day of symptoms starting • Given enough drugs for 50% of the population, household-based prophylaxis coupled with reactive school closure could reduce clinical attack rates by 40–50% • More widespread prophylaxis would be even more logistically challenging but might reduce attack rates by over 75%. • Vaccine stockpiled in advance of a pandemic could significantly reduce attack rates even if of low efficacy. A ‘Small-world-like’ Carat et 2006 BMC Influenza Epidemiological • Closing schools when the number of infections model for comparing al. Medicine (Pandemic) modelling to test in the community exceeded 5 per 1000 interventions aimed at impact of various community members (and not reopening until preventing and interventions of 10 days after the last observed case of controlling influenza spread of influenza infection) would be very effective, limiting the pandemics (including vaccination, size of outbreaks to 10% of the population treatment/prophylaxis (range 0.9%–22%). , quarantine, school • When workplaces and schools were closed (but closures and telework) for a shorter time than schools alone), infections were limited to 1% of the population (range 0.6-2.1) but resulted in substantially higher lost workdays.

Title Authors Year Journal Infectious Methods High-Level Results Disease Community mitigation Qualls et 2017 MMWR Influenza CDC guidelines • Categories of NPIs include personal protective guidelines to prevent al. (CDC (Pandemic) updates using lessons measures for everyday use; personal protective pandemic influenza — team) learned from H1N1 measures reserved for influenza pandemics ; United States, 2017 and case studies community measures aimed at increasing social distancing; and environmental measures • Underscores the importance of broad and flexible pre-pandemic planning • Community engagement has been included to highlight that the timely and effective use of NPIs depends on community acceptance and active participation

Title Authors Year Journal Infectious Methods High-Level Results Disease Travel Restrictions The effect of travel Chinazzi 2020 Science COVID-19 Epidemiological • The travel quarantine of Wuhan delayed the restrictions on the spread et al. modelling to project overall epidemic progression by only 3 to 5 days of the 2019 novel the impact of travel in Mainland China, but has a more marked coronavirus (COVID-19) limitations on the effect at the international scale, where case outbreak national and importations were reduced by nearly 80%, until international spread mid-February. of the epidemic. • While the Wuhan travel ban was initially effective at reducing international case importations, the number of cases observed outside Mainland China will resume its growth after 2-3 weeks from cases that originated elsewhere • Additional travel limitations up to 90% of the traffic restrictions to and from Mainland China have a modest effect unless paired with public health interventions and behavioral changes that achieve a considerable reduction (50% or higher) in the disease transmissibility in the community. • Even in the presence of the strong travel restrictions in place to and from Mainland China since 23 January 2020, a large number of individuals exposed to the SARS-CoV-2 have been traveling internationally without being detected • Travel restrictions to COVID-19 affected areas will have modest effects, and transmission- reduction interventions will provide the greatest benefit to mitigate the epidemic.

Title Authors Year Journal Infectious Methods High-Level Results Disease Effectiveness of travel Mateus 2014 Bulletin Influenza Systematic review to • Internal travel restrictions and international restrictions in the rapid et al. World assess evidence for border restrictions delayed the spread of containment of human Health restrictions in travel influenza epidemics by one week and two influenza: a systematic Organizati affecting the spread of months, respectively. review on influenza. • International travel restrictions delayed the spread and peak of epidemics by periods varying between a few days and four months • Travel restrictions reduced the incidence of new cases by less than 3%. • Impact was reduced when restrictions were implemented more than six weeks after the notification of epidemics or when the level of transmissibility was high. • Travel restrictions would have minimal impact in urban centers with dense populations and travel networks. • No evidence that travel restrictions would contain influenza within a defined geographical area. • Extensive travel restrictions may delay the dissemination of influenza but cannot prevent it

Title Authors Year Journal Infectious Methods High-Level Results Disease Cost and Economic Analyses The cost effectiveness of Milne et 2013 PLoS ONE Influenza cost effectiveness • Intervention strategies combining school pandemic influenza al. (Pandemic) analysis of social closure with antiviral treatment and prophylaxis interventions: A distancing and are the most cost-effective strategies in terms pandemic severity based antiviral drug of cost per life year saved (LYS) for all severity analysis strategies intended to categories. mitigate a future • With high severity pandemics (CFR .0.75%) the pandemic was most effective attack rate reduction strategies conducted using a are also the most cost effective. simulation model of a • During low severity pandemics costs are community of 30,000 dominated by productivity losses due to illness in Australia. and social distancing interventions, while for high severity pandemics costs are dominated by hospitalization costs and productivity losses due to death. • The most cost-effective strategies for mitigating an influenza pandemic involve combining sustained social distancing with the use of antiviral agents. Value for money in H1N1 Pasquini- 2017 Elsevier Influenza Review of 18 • hospital quarantine, vaccination, and usage of influenza: A systematic Descomp (Pandemic) academic articles that the antiviral stockpile are highly cost-effective, review of the cost- s et al. provide cost- even for mild pandemics effectiveness of effectiveness or cost- • However, school closures, antiviral treatments, pandemic interventions benefit analyses for and social distancing may not qualify as A/H1N1 pandemic efficient measures, for a virus like 2009's H1N1 interventions since and a willingness-to-pay threshold of $45,000 2009 per disability-adjusted life-year • Important to note: such interventions may become cost-effective for severe crises. • One should consider these results carefully, considering these may not apply to a specific crisis or country, and a dedicated cost- effectiveness assessment should be conducted at the time.

Title Authors Year Journal Infectious Methods High-Level Results Disease Systematic review of Perez 2012 PLoS ONE Influenza Systematic review of • Pharmaceutical plus non-pharmaceutical economic evaluations of Velasco (Pandemic) 44 studies interventions are relatively cost effective in preparedness strategies et al. comparison to vaccines and/or antivirals alone and interventions against • Pharmaceutical interventions vary from cost influenza pandemics saving to high cost effectiveness ratios. • According to ceiling thresholds (Gross National Income per capita), the reduction of nonessential contacts and the use of pharmaceutical prophylaxis plus the closure of schools are amongst the cost-effective strategies for all countries. • Quarantine for household contacts is not cost effective even for low- and middle-income countries. • The available evidence is generally inconclusive regarding the cost effectiveness of preparedness strategies and interventions against influenza pandemics. • Guidelines for assessing the impact of disease and interventions should be drawn up to facilitate these studies

Glossary of Key Terms Basic reproduction number (R 0 ): R 0 is used to describe the contagiousness or transmissibility of an infectious agent; also called the basic reproduction ratio, the basic reproduction rate, or the basic reproductive number. An infectious agent’s reproduction number may change over time, for example, due to the implementation of interventions and as immunity is established. The effective reproduction number, which differs from R 0 in that it does not assume complete susceptibility of the population, determines the ability of an infectious agent to have persistent or growing prevalence in a population (when the effective reproduction number is above 1 the disease will have growing prevalence; below 1 it will decline). The effective reproduction number can also be specified at a particular time, presented as Rt, which can be used to trace changes in the effective reproductive number as the number of susceptible members in a population is reduced. Case fatality rate (CFR): Case fatality rate is the proportion of people who die from a specified disease among all individuals diagnosed with the disease over a certain period of time. Cordon sanitaire: Cordon sanitaire is a strategy used to limit the spread of an infectious agent that involves curtailing the movement of individuals into and out of a defined geographical area where one or more infections have been identified. Such mobility restrictions historically were used to control infectious diseases, such as bubonic plague, and, more recently, to control the spread of Ebola in West Africa and SARS-CoV-2. Cumulative illness attack rate: Attack rate is the proportion of an initially disease-free population that develops disease, becomes injured, or dies during a specified (usually limited) period of time. Influenza-like illness (ILI): ILI is an acute respiratory illness with a fever (temperature of 100°F [37.8°C] or greater) and a cough and/or a sore throat without a known cause other than influenza. Modeling study: Modeling studies are widely used to help inform decisions in public health policy, and a model is an analytical methodology that accounts for events over time and across populations that is based on data drawn from primary or secondary sources. Non-pharmaceutical intervention (NPI): Non-pharmaceutical interventions are actions that people and communities can take to help slow the spread of illness or reduce the adverse impact of public health emergencies. NPIs may include isolation, quarantine, restrictions on movement and travel advisories or warnings, social distancing, external decontamination, hygiene, and precautionary protective behaviors. Rescinding threshold: A rescinding threshold is a cutoff for a pre-defined criterion (for example, incidence of newly identified cases) at which mitigation strategies (e.g., school closure) that have been implemented to control the spread of an infectious agent may be discontinued and/or relaxed.

Rapid Expert Consultation on Social Distancing for the COVID-19 Pandemic (March 19, 2020) Get This Book
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In response to a request from the Office of Science and Technology Policy (OSTP), the National Academies of Sciences, Engineering, and Medicine convened a standing committee of experts to help inform OSTP on critical science and policy issues related to emerging infectious diseases and other public health threats. The standing committee includes members with expertise in emerging infectious diseases, public health, public health preparedness and response, biological sciences, clinical care and crisis standards of care, risk communication, and regulatory issues. This publication provides feedback on questions about the effectiveness and costs of social distancing measures in contending with COVID-19.

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