Seroprevalence of anti-SARS-CoV-2 IgG antibodies pre- and post-COVID-19 vaccination in staff members of Bandar Abbas Children’s Hospital

Abstract Background Healthcare workers (HCWs) have a higher risk of contracting coronavirus disease 2019 (COVID-19) compared to the general population due to their frontline role and direct contact with the infected patients. Accordingly, they were among the first groups to receive vaccination against COVID-19. A higher risk of COVID-19 infection may also exist among hospital staff members other than HCWs. In this study, we assessed the seroprevalence of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG pre- and post-COVID-19 vaccination in hospital staff members. Methods This cross-sectional study included 228 staff members of Bandar Abbas Children’s Hospital, Bandar Abbas, Iran, who were recruited from 2020 to 2021. Staff members were vaccinated with vector and inactivated vaccines. Anti-SARS-CoV-2 spike protein IgG was measured in their blood samples pre- and post-COVID-19 vaccination. Results Of the 228 hospital staff members evaluated in this study (mean age: 37.59 ± 8.70 years), 204 (89.5%) were female and 210 (92.1%) were HCWs. Only one staff member was not vaccinated, the rest received one dose (99.6%), and 224 (98.7%) two doses. Vector vaccines were administered to 71.4% of staff members and 72.9% of HCWs. Anti-SARS-CoV-2 IgG antibody was positive in 8.8% of staff members before vaccination, 9.3% after the first dose, and 50% after the second dose. The corresponding percentages were 9.5%, 9.5%, and 48.8% in HCWs. Being a HCW was not associated with the seroprevalence of anti-SARS-CoV-2 IgG after the second dose; however, multivariable binary logistic regression analysis revealed that the interval between two vaccine doses (adjusted odds ratio [aOR] = 0.595, 95% confidence interval [CI] 0.434; 0.816, P = 0.001) and age (aOR = 1.062, 95% CI 1.021; 1.105, P = 0.003) were associated with seroprevalence. Conclusions After receiving a second dose of vector or inactive virus vaccines, our hospital’s staff members and HCWs had a seroprevalence of anti-SARS-CoV-2 IgG antibodies of around 50%. Seroprevalence increased with increasing age and shorter intervals between doses.