Covid-19 Mitigation With Appropriate Safety Measures In An Essential Workplace: Lessons For Opening Work Settings In The United States During Covid-19

Background. Nonpharmaceutical interventions (NPIs) mitigate coronavirus disease 2019 (COVID-19). Essential workplaces remained open during COVID-19, but few US-based settings detail outcomes.Methods. Mercury Systems is a US-based manufacturing company that remained open during COVID-19. NPIs-distancing, masking, hand hygiene, ventilation-were successively deployed from March to August 2020. The company expanded sick leave, asked employees to report work outages from illness, and administered employee satisfaction surveys. Three sites in Arizona, Southern California, and New Hampshire administered testing campaigns via reverse transcription polymerase chain reaction (PCR) of nasal swabs in late July to early August for all employees at work or at home self-isolating due to symptoms. Descriptive statistics summarized findings.Results. Among 586 employees at 3 sites, only 1.5% employees developed severe illness over the study duration. Testing campaigns revealed 44 with positive PCR results at a cycle threshold (CT) <37 (likely infectious) and 61 with a CT >= 37 (low-level viral load). True positivity rates were consistent with community prevalence at the time: 1.1% in New Hampshire, 6.2% in California, 12.9% in Arizona. Of all employees with positive tests, 99% were asymptomatic. Employee surveys showed high satisfaction.Conclusions. In a multisite US company that instituted NPIs for COVID-19 mitigation, the proportion of asymptomatic COVID-19 infections on surveillance testing was high (99%). Although surges in community transmission were seen in 2 sites during the study, employee prevalence reflected community prevalence, despite daily workplace presence. This study demonstrates that NPIs likely mitigate severe COVID-19 illness, that PCR tests should incorporate CT values, and that expanded sick leave likely encourages self-isolation, suggesting strategies for work re-openings.