Screening for high amounts of SARS-CoV-2 identifies pre-symptomatic subjects among healthy healthcare workers

BackgroundPre-symptomatic subjects are spreaders of SARS-CoV-2 infection, and strategies that could identify these subjects, particularly in hospital settings, are needed. MethodsWe tested a cohort of 9449 employees at work at the Karolinska University Hospital, Stockholm, Sweden for SARS-CoV-2 RNA and antibodies, linked the screening results to sick leave records and examined the association between screening results and past or future sick leave using multinomial logistic regression. ResultsWe found that healthcare workers with high amounts of SARS-CoV-2 virus, as indicated by the Cycle threshold (Ct) value in the PCR, had the highest risk for sick leave in the two weeks after testing (OR 11{middle dot}97 (CI 95% 6{middle dot}29-22{middle dot}80)) whereas subjects with low amounts of virus had the highest risk for sick leave in the past three weeks before testing (OR 6{middle dot}31 (4{middle dot}38-9{middle dot}08)). Only 2{middle dot}5% of employees were SARS-CoV-2 positive while 10{middle dot}5% were positive by serology and 1{middle dot}2% were positive in both tests. Serology-positive subjects were not at excess risk for future sick leave (OR 1{middle dot}06 (95% CI, 0{middle dot}71-1{middle dot}57)), but virus-positive subjects had a 7{middle dot}23 fold (95% CI, 4{middle dot}52-11{middle dot}57)) increased risk for sick leave within two weeks post testing. ConclusionsScreening of asymptomatic healthcare workers for high amounts of SARS-CoV-2 virus using Ct values will identify pre-symptomatic subjects who will develop disease in the next few weeks. Identification of potentially contagious, pre-symptomatic subjects is likely critical for protecting patients and healthcare workers. Main pointHealthy healthcare workers with low amounts of SARS-CoV-2 nucleic acids will previously have had the disease. Presence of a high amount of SARS-CoV-2 nucleic acids predicts future symptomatic disease.

Antibodies to SARS-CoV-2 and risk of future sickness

Background: The extent that antibodies to SARS-CoV-2 may protect against future virus-associated disease is unknown. Method: We analyzed 12928 healthy hospital employees for SARS-CoV-2 antibodies and compared results to participant sick leave records (Clinical trial registration: ClinicalTrials.gov NCT04411576). Results: Subjects with viral serum antibodies were not at excess risk for future sick leave (Odds Ratio (OR): 0.85 (95% Confidence Interval (CI) (0.85 (0.43-1.68)). By contrast, subjects with antibodies had an excess risk for sick leave in the past weeks (OR: 3.34 (2.98-3.74)). Conclusion: Presence of viral antibodies marks past disease and protection against excess risk of future disease.