Random sampling of asymptomatic hospital employees: A period prevalence study

ABSTRACT

Background: Novel coronavirus disease 2019 (COVID-19) has had a significant impact on the work force in hospital settings. Despite rigorous screening practices implemented at many institutions, reports have documented transmission from asymptomatic and presymptomatic individuals in community environments. Evidence of nosocomial transmission between healthcare workers and patients in the early phase of the pandemic has further compounded the fears of safety in the workplace. We sought to determine the asymptomatic carriage rate of employees to inform messaging and response in the context of universal masking and eye protection. Methods: We conducted a period prevalence study in asymptomatic hospital employees at a quaternary pediatric hospital during April to June 2020. Eligible employees included clinical staff, administrative staff, food services workers, and environmental services workers who had passed the temperature and symptom screening evaluation on entry to the campus. Samples were obtained from both nares of consenting individuals and ran daily on a validated polymerase chain reaction (PCR) platform. Results: A total of 1394 employees consented to participate by June 15, 2020 and none of them had a positive result for COVID-19. Thus, the prevalence rate among asymptomatic employees was zero during this period (95%CI 0%-0.26%). Thirteen employees developed symptoms after initial enrollment and testing of which 1 tested positive for COVID-19. Based on these data, we estimate a monthly incidence rate of 0.8 new COVID-19 cases per 1000 asymptomatic employees (95%CI 0.2 - 4.4 per 1000). Of note, at the time of submission the R0 for our region was 1.4, and the prevalence of COVID-19 infection among symptomatic employees was 9.9% (68/686 tested in our system, 95%CI 7.8%-12.3%). Conclusion: We did not identify any COVID-19-positive asymptomatic hospital employees who passed screening measures. This suggests very low risk of nosocomial transmission to other employees, patients, and families. Along with low community prevalence and capture of COVID-19-positive symptomatic employees, we could confidently advise staff that universal surgical masking and eye protection were likely adequate to prevent significant exposure.