Human serum samples used in this study
A total of 53 serum samples of poultry farm personnel collected between August and September 2020 were used in this study. These samples were obtained from actively appointed personnel in four commercial poultry farms located in the Aegean and Marmara regions of Turkey. The samples were categorized into two groups. The first group (n=39) consisted of vaccine implementers who administer IBV live attenuated vaccines through aerosol spraying in the poultry house. The second group (n=14) comprises poultry workers, who collect the meat-type chickens before slaughter and raise the chickens in the poultry house. The mean age of poultry farm personnel was 31.53 ± 1.07 years. Of the 53 individuals, 51 were male. Concerning vaccine implementers (sample numbers from VI1 to VI39), mean work experience was 80.4 ± 14.4 months. The mean work experience for poultry workers (sample numbers from PW1 to PW14) was 81.1 ± 23.6 months (Table S1). In addition, sera from healthy voluntary donors (n=38) obtained in the pre-pandemic era (i.e. before October 2019) were used as negative controls. RT-PCR-confirmed non-hospitalized (n=19) (sample numbers from C1 to C19) and hospitalized COVID-19 patient samples (n=18) (sample numbers from C20 to C37) were used as positive controls. Together, the COVID-19 patient cohort had a mean age of 42.86 ± 2.29 years and 35.14% of the patients were female. Demographics of poultry farm personnel, COVID-19 patients, and pre-pandemic controls are shown in Tables S1, S2, and S3, respectively. Following written informed consent, all participants provided blood specimens for analysis. The study protocol was approved by the Ethics Committees of the Bursa Uludag University of Turkey (2021-11/13) and the Ethics Committee of Zurich (2020-00898 and 2020-01322).