ABSTRACT
IntroductionSince March of 2020, over 210 million SARS-CoV-2 cases have been reported and roughly five billion doses of a SARS-CoV-2 vaccine have been delivered. The rise of the more infectious delta variant has recently indicated the value of reinstating previously relaxed non-pharmacological and test-driven preventative measures. These efforts have been met with resistance, due, in part, to a lack of site-specific quantitative evidence which can justify their value. As vaccination rates continue to increase, a gap in knowledge exists regarding appropriate thresholds for escalation and de-escalation of COVID-19 preventative measures. MethodsWe conducted a series of simulation experiments, trialing the spread of SARS-CoV-2 virus in a hypothesized working environment that is subject to COVID-19 infections from the surrounding community. We established cohorts of individuals who would, in simulation, work together for a set period of time. With these cohorts, we tested the rates of workplace and community acquired infections based on applied isolation strategies, community infection rates (CIR), scales of testing, non-pharmaceutical interventions, variant predominances and testing strategies, vaccination coverages, and vaccination efficacies of the members included. Permuting through each combination of these variables, we estimated expected case counts for 33,462 unique workplace scenarios. ResultsWhen the CIR is 5 new confirmed cases per 100,000 or fewer, and at 50% of the workforce is vaccinated with a 95% efficacious vaccine, then testing daily with an antigen-based or PCR based test in only unvaccinated workers will result in less than one infection through 4,800 person weeks. When the community infection rate per 100,000 persons is less than or equal to 60, and the vaccination coverage of the workforce is 100% with 95% vaccine efficacy then no masking or routine testing + isolation strategies are needed to prevent workplace acquired infections regardless of variant predominance. Identifying and isolating workers with antigen-based SARS-CoV-2 testing methods results in the same or fewer workplace acquired infections than testing with polymerase chain reaction (PCR) methods. ConclusionsSpecific scenarios exist in which preventative measures taken to prevent SARS-CoV-2 spread, including masking, and testing plus isolation strategies can safely be relaxed. Further, efficacious testing with quarantine strategies exist for implementation in only unvaccinated cohorts in a workplace. Due to shorter turnaround time, antigen-based testing with lower sensitivity is more effective than PCR testing with higher sensitivities in comparable testing strategies. The general reference interactive heatmap we provide can be used for site specific, immediate, parameter-based case count predictions to inform appropriate institutional policy making.
Subject(s)
COVID-19ABSTRACT
Background: Until herd immunity occurs for COVID-19, quarantine will remain a pillar for disease mitigation. A 14-day quarantine, although widely recommended for self-quarantine after potential infections and mandated by many government agencies can be physically and mentally stressful for those under quarantine and leads to lost productivity. Testing during quarantine is currently implemented by businesses and governments as a promising method to shorten the duration of quarantine. However, to our knowledge, no study has been performed to evaluate the performance of test-assisted quarantines and to identify the most effective choices of testing schedule. Methods: Based on statistical models for the transmissibility and viral loads of SARS-CoV-2 infections and sensitivity of various SARS-CoV-2 tests, we performed extensive simulations to evaluate the performance of quarantine strategies with one or more tests administered during quarantine. Sensitivity analyses were performed to evaluate the impact of model assumptions on the selection of optimal strategies. Findings: We found that SARS-CoV-2 testing can effectively reduce the length of quarantine without compromising safety. Whereas a single RT-PCR test performed before the end of quarantine can reduce the duration of quarantine to 10 days, two tests can further reduce the duration to 8-days and three tests with a highly sensitive RT-PCR test can justify a 6-day quarantine. More strategic testing schedules and one more day of quarantine are needed if tests are administrated with a less sensitive but more cost-effective antigen test. Interpretation: Testing during quarantine could substantially reduce the length of quarantine, reducing the physical and mental stress caused by long quarantines. With increasing capacity and lowered costs of SARS-CoV-2 tests, testing-assisted quarantines could be safer and more cost-effective than 14-day quarantines and warrant more widespread use.