Influencing factors of anti‐SARS‐CoV‐2‐spike‐IgG antibody titers in healthcare workers: A cross‐section study

Against the background of the current COVID‐19 infection dynamics with its rapid spread of SARS‐CoV‐2 variants of concern (VOC), the immunity and the vaccine prevention of healthcare workers (HCWs) against SARS‐CoV‐2 continues to be of high importance. This observational cross‐section study assesses factors influencing the level of anti‐SARS‐CoV‐2‐spike IgG after SARS‐CoV‐2 infection or vaccination. One thousand seven hundred and fifty HCWs were recruited meeting the following inclusion criteria: age ≥18 years, PCR‐confirmed SARS‐CoV‐2 infection convalescence and/or at least one dose of COVID‐19 vaccination. anti‐SARS‐CoV‐2‐spike IgG titers were determined by SERION ELISA agile SARS‐CoV‐2 IgG. Mean anti‐SARS‐CoV‐2‐spike IgG levels increased significantly by number of COVID‐19 vaccinations (92.2 BAU/ml for single, 140.9 BAU/ml for twice and 1144.3 BAU/ml for threefold vaccination). Hybrid COVID‐19 immunized respondents (after infection and vaccination) had significantly higher antibody titers compared with convalescent only HCWs. Anti‐SARS‐CoV‐2‐spike IgG titers declined significantly with time after the second vaccination. Smoking and high age were associated with lower titers. Both recovered and vaccinated HCWs presented a predominantly good humoral immune response. Smoking and higher age limited the humoral SARS‐CoV‐2 immunity, adding to the risk of severe infections within this already health impaired collective.