Occupational Risk Factors for SARS-CoV-2 Infection in Hospital Health Care Workers: A Prospective Nested Case-Control Study.

Introduction: Health Care Workers (HCWs) are at a particular high risk of SARS-CoV-2 infection due to direct and indirect exposure to COVID-19 patients and Aerosol-Generating Procedures (AGPs). The aim of the study was to assess the risk factors for SARS-CoV-2 infection in HCWs exposed to COVID-19 patients, to evaluate the adherence and effectiveness of Infection Prevention and Control (IPC) measures, to describe the clinical presentation for SARS-CoV-2 infection in HCWs and to determine serological responses in HCWs. Methods: HCWs exposed to COVID-19 patients during the previous 14 days with a confirmed case status were recruited as cases; HCWs exposed to COVID-19 patients during the previous 14 days in the same ward without a suspected/probable/confirmed case status were recruited as controls. Serum samples were collected as soon as possible and after 21-28 days from all participants. Data were collected with a WHO standardized questionnaire as soon as possible and after 21-28 days. Results: All social, occupational and personal variables considered were not associated with an increased risk of SARS-CoV-2 infection. Conclusions: Our study showed a high knowledge of IPC measures and very high PPE use among HCWs.

Low sensitivity of rapid tests detecting anti-CoV-2 IgG and IgM in health care workers' serum for COVID-19 screening.

BACKGROUND: the sensitivity and specificity of a rapid antibody test were investigated for the screening of healthcare workers. METHODS: the serum of 389 health care workers exposed to COVID-19 patients or with symptoms, were analysed. All workers underwent monthly the screening for SARS-CoV-2 with detection of viral RNA in nasopharyngeal swabs by RT-PCR. IgG antibody detection in serum was performed by Chemiluminescence Immunoassay (CLIA) and by the Rapid test (KHB diagnostic kit for SARS CoV-2 IgM/IgG antibody after a median of 7.6 weeks (25°-75° percentiles 6.6-11.5). RESULTS: the rapid test resulted positive in 31/132 (23.5%), 16/135 (11.8%) and 0/122 cases in COVID-19 positive individuals, in those with only SARS-CoV-2 IgG antibodies and in those negative for both tests, respectively. Sensitivity was 17.6% (CI95% 13.2-22.7) and 23.5% (CI95% 16.5-31.6), and specificity was 100% (CI95% 97-100) and 100% (CI95% 97-100) considering Rapid test vs CLIA IgG or Rapid test vs SARS-CoV-2 positive RNA detection, respectively. CONCLUSION: the KHB Rapid test is not suitable for the screening of workers with previous COVID-19 infection.