COVID Testing in the Workplace: Return to Work Testing in an Occupational Cohort

BackgroundThe Omicron SARS-CoV-2 variant resulted in significant community-based transmission. Numerous occupational settings have employed surveillance testing strategies to minimize occupational exposure and return workers safely to work following isolation. MethodsFrom an occupational COVID-19 testing program, we obtained longitudinal (February 2021-January 2022) saliva-based RT-qPCR results and starting December 27th, 2021, daily on-site molecular over-the-counter (OTC) nasal swab-based isothermal nucleic acid amplification test (molecular OTC; Cue Health COVID-19 test) results. We quantified the fraction of tests with PCR cycle threshold (Ct) values <30 on each day post detection from suspected and confirmed Omicron infections (n=37), compared results to molecular OTC testing, and measured workplace and household transmission. We evaluated return-to-work timing using a post-isolation, two-test threshold of Ct >30, or two negative molecular OTC tests over a 24 hour period, or a single PCR test >30 plus negative molecular OTC test. ResultsFrom the paired testing cohort, 37 (48%) individuals tested positive; all 37 were vaccinated. All individuals tested positive [&le;]1 day after a previous negative test, and 19 (51.3%) remained PCR-positive with Ct values <30 at day 5. While 3 (8.1%) remained PCR-positive with a Ct value <30 on day 10, no individuals remained PCR-positive on day 12. The average time to PCR clearance/return-to-work was 7.94 days (median=9.5 days). Time to clearance for those boosted (n=8; 7.75 days) and those not yet boosted (8.04 days) did not differ (p=0.49). Peak viral load measured by PCR was 1.97 days from the initial positive test. There were no cases of transmission after returning to work. ConclusionsA large percentage of individuals remain contagious at day 5 post first positive test based on serial PCR testing and can continue until day 12. Early discontinuation of isolation can utilize a two test framework separated by 24 hours. Rapid onsite tests may be useful.