Quantitation of antibodies against SARS‐CoV‐2 spike protein after two doses of CoronaVac in healthcare workers

Quantitation of antibodies to the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) was performed for the detection of adaptive immune response in healthcare workers (HCWs) vaccinated with CorovaVac. We prospectively recruited HCWs from a university hospital in Turkey. Serum samples from 1072 HCWs were obtained following 28 days of the first, and 21 days of the second dose. Detection and quantitation of SARS‐CoV‐2 antispike antibodies were performed by the chemiluminescent microparticle immunoassay (SARS‐CoV‐2 IgG II Quant; Abbott). Results greater than or equal to the cutoff value 50.0 AU/ml were reported as positive. After the first dose, antispike antibodies were detected in 834 of 1072 (77.8%) HCWs. Seropositivity was higher among females (84.6%) than males (70.6%) (p