key: cord-283409-ynwgdz52 authors: Baggett, Travis P.; Scott, Justine A.; Le, Mylinh H.; Shebl, Fatma M.; Panella, Christopher; Losina, Elena; Flanagan, Clare; Gaeta, Jessie M.; Neilan, Anne; Hyle, Emily P.; Mohareb, Amir; Reddy, Krishna P.; Siedner, Mark J.; Harling, Guy; Weinstein, Milton C.; Ciaranello, Andrea; Kazemian, Pooyan; Freedberg, Kenneth A. title: Clinical Outcomes, Costs, and Cost-effectiveness of Strategies for People Experiencing Sheltered Homelessness During the COVID-19 Pandemic date: 2020-10-20 journal: medRxiv DOI: 10.1101/2020.08.07.20170498 sha: doc_id: 283409 cord_uid: ynwgdz52 IMPORTANCE: Approximately 356,000 people stay in homeless shelters nightly in the US. They are at high risk for COVID-19. OBJECTIVE: To assess clinical outcomes, costs, and cost-effectiveness of strategies for COVID-19 management among sheltered homeless adults. DESIGN: We developed a dynamic microsimulation model of COVID-19 in sheltered homeless adults in Boston, Massachusetts. We used cohort characteristics and costs from Boston Health Care for the Homeless Program. Disease progression, transmission, and outcomes data were from published literature and national databases. We examined surging, growing, and slowing epidemics (effective reproduction numbers [R(e)] 2.6, 1.3, and 0.9). Costs were from a health care sector perspective; time horizon was 4 months, from April to August 2020. SETTING & PARTICIPANTS: Simulated cohort of 2,258 adults residing in homeless shelters in Boston. INTERVENTIONS: We assessed daily symptom screening with polymerase chain reaction (PCR) testing of screen-positives, universal PCR testing every 2 weeks, hospital-based COVID-19 care, alternate care sites [ACSs] for mild/moderate COVID-19, and temporary housing, each compared to no intervention. MAIN OUTCOMES AND MEASURES: Cumulative infections and hospital-days, costs to the health care sector (US dollars), and cost-effectiveness, as incremental cost per case prevented of COVID-19. RESULTS: We simulated a population of 2,258 sheltered homeless adults with mean age of 42.6 years. Compared to no intervention, daily symptom screening with ACSs for pending tests or confirmed COVID-19 and mild/moderate disease led to 37% fewer infections and 46% lower costs (R(e)=2.6), 75% fewer infections and 72% lower costs (R(e)=1.3), and 51% fewer infections and 51% lower costs (R(e)=0.9). Adding PCR testing every 2 weeks further decreased infections; incremental cost per case prevented was $1,000 (R(e)=2.6), $27,000 (R(e)=1.3), and $71,000 (R(e)=0.9). Temporary housing with PCR every 2 weeks was most effective but substantially more costly than other options. Results were sensitive to cost and sensitivity of PCR and ACS efficacy in preventing transmission. CONCLUSIONS & RELEVANCE: In this modeling study of simulated adults living in homeless shelters, daily symptom screening and ACSs were associated with fewer COVID-19 infections and decreased costs compared with no intervention. In a modeled surging epidemic, adding universal PCR testing every 2 weeks was associated with further decrease in COVID-19 infections at modest incremental cost and should be considered during future surges. In this supplemental appendix, we provide additional model inputs, results from one-way and multi-way sensitivity analyses, and scaled results for a cohort of 1,000 adults experiencing sheltered homelessness. In addition, we provide details on the Clinical and Economic Analysis of COVID-19 interventions (CEACOV) model and management strategies for people experiencing sheltered homelessness. CEACOV simulates individuals transitioning between the states of susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), infection with SARS-CoV-2 and coronavirus disease 2019 illness, recovery, or death. Susceptible individuals face a daily probability of acquiring infection. After acquiring SARS-CoV-2 infection, individuals may progress through the following health states (eFigure 1): • Pre-infectious latency • Asymptomatic infection • Mild/moderate illness: symptomatic • Severe illness: dyspnea and/or hypoxemia ideally managed in a hospital with standard supplemental oxygen but not requiring intensive care unit (ICU) • Critical illness: ideally managed in an ICU with high-flow supplemental oxygen, non-invasive positive pressure ventilation, or invasive mechanical ventilation • Recuperation: for those recuperating from critical illness and improving while remaining in the hospital or other health care facility • Recovered Individuals in the asymptomatic infection, mild/moderate illness, and severe illness states can transition directly to the recovered state. Individuals in the critical illness state can eventually die, or transition to the recuperation state and then to the recovered state. The recovered state is an absorbing state, and recovered individuals are assumed to have immunity to SARS-CoV-2 over the model time horizon. After being infected with SARS-CoV-2, a susceptible individual first transitions to the pre-infectious latency stage. Then, the individual has an age-dependent probability of progressing along one of four "paths," culminating in either asymptomatic infection, mild/moderate illness, severe illness, or critical illness. Before reaching a more advanced illness state, individuals first transition through intermediate states (e.g., those destined for severe illness must first pass through the asymptomatic infection state and the mild/moderate illness state, eFigure 1). In CEACOV, infected individuals in mild/moderate, severe, critical, and recuperation states can transmit SARS-CoV-2 to susceptible individuals. The effective transmission rate of infected individuals in one of these states is calculated as follows: The nominal transmission rate (Rnom) is a function of the average number of susceptible persons whom an infected individual contacts per day in a fully susceptible cohort multiplied by the probability of infecting the susceptible person per contact. This nominal transmission rate captures the ratio of daily infectivity stratified by illness states. The effective magnitude of the transmission rate, however, changes over time as social interventions alter the daily average number of contacts between susceptible and infected individuals as well as the infectivity per contact. Hence, the transmission multiplier is leveraged to adjust the magnitude. Transmission multipliers are setting-specific, time-dependent adjusting factors, roughly accounting for population density and interventions that can alter the number of contacts (e.g., social distancing) and the infectivity per contact (e.g., masking) in the setting being modeled. In this analysis, the transmission multipliers were calibrated to represent a surging, a growing, and a slowing epidemic. Given the time-dependent uptake of such policies, timevarying transmission multipliers may be used to alter the effective transmission rate (Reff) over time. Reff determines the effective transmission rate of infected individuals on each day of simulation and is equivalent to the effective reproduction number (Re) divided by the duration of infectivity. Therefore, the effective transmission rate (Reff) in CEACOV and the effective reproduction number (Re) are directly related. In this analysis, we assumed that all susceptible persons have an equal probability of contacting infected individuals and acquiring the virus (i.e., homogenous mixing). As the epidemic grows, the number of susceptible persons declines. Thus, not all of the daily contacts of infected individuals will be with susceptible persons. The daily infection rate for a susceptible person is equal to the sum of transmission rates from all infected persons across all infection states divided by the cohort size. This leads to an expected daily number of infections equal to the number of susceptible people multiplied by the infection rate on that day. 7 eTable 1. Additional input parameters for an analysis of management strategies for people experiencing sheltered homelessness during the COVID-19 pandemic. *To obtain the initial illness distribution, we seeded the model with 0.01% of the starting cohort infected with the SARS-CoV-2 virus. We simulated the model for 10 days until the prevalence of SARS-CoV-2 in the cohort reached 2.2%. We used the illness distribution on Day 10 from this initialization run to inform our initial illness distribution in all model runs. Abbreviations: ACS, alternate care sites; Dominated, less clinically effective and more costly than an alternative strategy, or with a higher incremental cost-effectiveness ratio than another strategy; 15 Incr., incremental; SxScreen, symptom screen; TempHousing, temporary housing; UniversalPCR, polymerase chain reaction test for everyone; USD, United States dollars. Strategies are listed in order of ascending costs, per convention of cost-effectiveness analysis. City-specific population sizes of sheltered homeless adults are as follows: 2,258 in Boston, 1, 343 in Houston, 2, 053 in Chicago, 2, 770 in Philadelphia, 3, 556 in Seattle, 6, 945 in Los Angeles, and 31, 805 in New York. 16 * Costs were rounded to the nearest thousands. SARS-CoV-2), infection with SARS-CoV-2 and coronavirus illness 2019 (COVID-19), recovery from COVID-19, and death. Susceptible individuals face a daily probability of infection. After acquiring SARS-CoV-2 infection, individuals may progress through the following health states: pre-infectious latency, asymptomatic infection Then, the individual has an age-dependent probability of progressing along one of four "paths," culminating in either asymptomatic infection, mild/moderate illness, severe illness, or critical illness. Before a reaching a more advanced illness state Abbreviations: Asympt., asymptomatic; CEACOV, Clinical and Economic Analysis of COVID-19 interventions model Mild/Mod., mild/moderate NoIntervention: Only basic infection control practices are implemented in shelters CDC-recommended symptom screening daily in shelters. 6 Screen-negative individuals remain in shelters. Screen-positive individuals are sent to the hospital for PCR testing. PCR-positive individuals remain in hospital CDC-recommended symptom screening daily in shelters. Screen-negative individuals remain in shelters. Screen-positive individuals are sent to an ACS for people under investigation, where they undergo PCR testing and await results. PCR-positive individuals with mild/moderate illness are transferred to ACSs for confirmed COVID-19 cases Those with symptoms at the time of testing await results at the hospital; individuals without symptoms await results in shelters. PCR-negative individuals return to or stay in shelters. PCR-positive individuals, regardless of illness severity Those with symptoms at the time of testing are sent to an ACS for people under investigation while awaiting results; individuals without symptoms await results in shelters. PCR-negative individuals return to or stay in shelters. PCR-positive individuals with mild/moderate illness are All shelter residents are moved to temporary housing for the duration of the simulation. Universal PCR testing occurs every 2 weeks. PCR-positive individuals with mild/moderate illness remain in temporary housing and are transferred to the hospital if they progress to severe or critical disease Hybrid/Hospital: This includes the SxScreen/PCR/Hospital strategy, and adds universal PCR testing every 2 weeks in the shelter for those without symptoms This includes the SxScreen/PCR/ACS strategy, and adds universal PCR testing every 2 weeks in the shelter for those without symptoms In all 8 strategies, people with severe or critical illness are sent to the hospital. Individuals are eligible for repeat PCR testing after 5 days since their most recent negative test Abbreviations: ACS, alternate care sites UniversalPCR, universal polymerase chain reaction test for everyone Strategies are listed in order of ascending costs, per convention of cost-effectiveness analysis.