ABSTRACT
Introduction: Health care workers (HCW) are exposed to SARS-CoV-2 through patient contact. Objectives: We aimed to assess the seroprevalence for SARS-CoV-2 among HCW in the canton Grisons and analyze risk factors associated with seroconversion. Methods: HCW from 13 health care institutions were recruited. Sera were analyzed for SARS-CoV-2 antibodies using an electro-chemiluminescence immunoassay of Roche Diagnostics in mid-2020 (survey I) and early 2021 (survey II). Participants reported risk factors for COVID-19 in a questionnaire.Odds ratios (OR) and 95% confidence intervals (95% CI) for the association of seropositivity with each risk factor were determined by logistic regression. Results: SARS-CoV2 serology was positive in 99 of 2794 (3.5%) participants in survey I and in 376 of 2315 (13.5%) participants in survey II. By survey II, 86 of 88 (97.7%) initially seropositive participants remained seropositive. In multivariable analysis of both surveys, the strongest association for SARS-CoV-2 seroconversion was contact with a household member with COVID-19 (adjusted OR: 21.2, 95% CI: 8.5-51.4, p < 0.001, survey I;aOR: 8.5, 95% CI: 6.0-12.1, p < 0.001, survey II). Significant occupational risk factors included contact with patients with COVID-19 in both surveys (aOR: 2.7, 95% CI: 1.4-5.4, p < 0.001, survey I and aOR: 1.4, 95% CI: 1.0-2.2, p = 0.046, survey II). Contact to a SARSCoV- 2 positive co-worker was a significant risk factor only in survey I, whereas private contact with SARS-CoV-2 positive persons and the COVID-19 incidence in the region of the HCI were associated with seroconversion only in survey II. Conclusion: Contact with patients with COVID-19 was an important risk factor for seroconversion, although the risk was higher for household contacts. These findings highlight the need to optimize preventive measures for SARS-CoV2 infection among HCW.
ABSTRACT
Aim: We aimed to determine the distribution of WHO-standardized quantitative measurements of pan-immunoglobulin titers against the receptor binding domain of the SARS-CoV-2 spike protein following SARSCoV- 2 infection. Design & Methods: In a retrospective analysis we analyzed anonymized routine data of patient samples with SARS-CoV-2 infection, as evidenced with a pan-immunoglobulin assay directed against nucleocapsid-antigen measured with an electrochemiluminescence immunoassay (ECLIA;Roche Diagnostics, Switzerland). Pan-immunoglobulin titers of antibodies directed against the receptor binding domain of the SARS-CoV-2 spike protein were measured with the same technology. Results are given as binding antibody units (BAU) per mL. Cut-off for positivity is >0.8 BAU/mL Results: A total of 1436 samples originating from patients (635 males;801 females) aged 52 (median, interquartile range, IQR, [38,64]) years were included. There was no correlation between age and antibody titers Females (111, IQR [27,>257] BAU/mL) had significantly lower median antibody titers than males (147, IQR [36,>257] BAU/mL;p = 0.03) The antibody levels at the 2.5, 5, 10, 25, 68th percentiles were 1,3,6,27 and >257 BAU/ml, in females. The antibody levels at the 2.5, 5, 10, 25 62nd percentiles were 0.4, 2, 9, 36, and >257 BAU/ml in males Conclusions: Among patients with evidence of past SARS-CoV-2 infection one third exhibits antibody titers above the upper quantification limit (i.e. 257 BAU/mL). Fifteen percent of female and 12% of male patients have antibody titers of 10 BAU/mL or lower.