ABSTRACT
Healthcare workers (HCWs) are a risk group for SARS-CoV-2 infection, but which healthcare work that conveys risk and to what extent such risk can be prevented is not clear. Starting on April 24th, 2020, all employees at work (n=15,300) at the Karolinska University Hospital, Stockholm, Sweden were invited and 92% consented to participate in a SARS-CoV-2 cohort study. Complete SARS-CoV-2 serology was available for n=12,928 employees and seroprevalences were analyzed by age, sex, profession, patient contact, and hospital department. Relative risks were estimated to examine the association between type of hospital department as a proxy for different working environment exposure and risk for seropositivity, adjusting for age, sex, sampling week, and profession. Wards that were primarily responsible for COVID-19 patients were at increased risk (adjusted OR 1.95 (95% CI 1.65-2.32) with the notable exception of the infectious diseases and intensive care units (adjusted OR 0.86 (95% CI 0.66-1.13)), that were not at increased risk despite being highly exposed. Several units with similar types of work varied greatly in seroprevalences. Among the professions examined, nurse assistants had the highest risk (adjusted OR 1.62 (95% CI 1.38-1.90)). Although healthcare workers, in particular nurse assistants, who attend to COVID-19 patients are a risk group for SARS-CoV-2 infection, several units caring for COVID-19 patients had no excess risk. Large variations in seroprevalences among similar units suggest that healthcare work-related risk of SARS-CoV-2 infection may be preventable.
ABSTRACT
BackgroundIn March 2020, Stockholm, Sweden was hit by a severe outbreak of SARS-CoV-2. Four weeks later, a systematic study of testing for past or present infections among healthcare workers in the region was launched. Only a minority of COVID-19 related deaths occurred at hospitals and the study was therefore extended to employees in companies providing home care services for the elderly. MethodsFive companies offered participation to 438 employees at work and 405 employees (92.5%) were enrolled. Serum samples were analyzed for IgG to SARS-CoV-2 and throat swabs were tested by for the SARS-CoV-2 virus by PCR. ResultsAmong home care employees, 20.1% (81/403) were seropositive, about twice as many as in a simultaneously enrolled reference population (healthcare workers entirely without patient contact, n=3,671; 9.7% seropositivity). Only 13/379 employees (3.4%) had evidence of a current infection (PCR positivity). Among these, 5 were also seropositive (a sign of past infection or lingering infection after symptoms have resolved) and 3 were positive with only low amounts of virus. The combination of high amounts of virus and no antibodies, a characteristic for pre-symptomatic COVID-19, was thus present only in 5 employees (1.3%). ConclusionsPersonnel providing home service for the elderly appear to be a risk group for SARS-CoV-2 infection. Employees likely to be pre-symptomatic for COVID-19 can be readily identified by screening. Increased attention for protection of employees as well as of the elderly they serve is warranted.
ABSTRACT
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.
ABSTRACT
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.
