الفهرس 
Immunity against TB in health care workers and its relation to SARS-CoV-2 viral infection
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Abstract
Health care workers are at high risk of exposure to various infectious diseases including Mycobacterium tuberculosis and SARS-CoV-2. Countries with BCG vaccination policies and with higher rate of TB exposure were shown to have lower infection and mortality rate due to COVID-19. This observation maybe attributed to the non-specific effect that BCG vaccine has demonstrated against other viral infections.
Aim: To assess immunity against TB in a cohort of Kasr El-Aini Medical hospital health care workers and SARS-CoV-2 infection and evaluate the relation between positive tuberculin skin testing and SARS-CoV-2 viral infection and the possible protective role of BCG vaccination in prevention of SARS-CoV-2 infection.
Materials and methods: Cross sectional study was conducted on 65 health care workers in Kasr Al-Aini Medical hospital. Tuberculin skin test (TST) was done using the Mantoux method and serum was tested for SARS-CoV2 antibody titer for IgM and IgG using chemiluminescent immunoassay (CLIA). The studied HCW were classified according to their TST results into two groups; non-immune against TB (induration < 10mm) and immune against TB (induration ≥ 10mm) and according to antibody positivity into non- previously and previously infected with SARS-CoV-2.
Results: We report that 33.8% of the participating HCW had positive TST results, 40% had documented history of SARS-CoV-2 infection by a positive swab for viral RNA and 63.1% had positive SARS-CoV-2 IgG. Mild SARS-CoV-2 infection was reported in 52% of the symptomatic participants and asymptomatic infection was reported by SARS-CoV-2 IgG in 38.4%. No statistical significant relation between TST and SARS-CoV-2 IgG. Multivariate logistic regression analysis revealed statistically significant relation between the SARS-CoV-2 IgG in non-smokers and nurses with p value 0.021 and 0.015 respectively.
Conclusion: The hypothesis of the possible protective role of BCG vaccination in prevention of CoV-2 infection could not be proved. Besides, more attention should be given to Nurses being the most affected group by SARS-CoV-2 infection by providing sufficient infection control measures and vaccination