Study cohort
A total of 56 samples from 43 individuals vaccinated with SARS-CoV-2 vaccines were enrolled in this study. The ages of vaccinated subjects were ranging between 21 and 32 years. The vaccinated donors who were suffering from infectious diseases or autoimmune diseases, and experiencing any inflammation or infection within a week before sampling were excluded from this study. Subjects were divided into three groups according to different types of vaccine they received, including inactivated vaccine group (CoronaVac, Sinovac Biotech, China), recombinant protein subunit vaccine group (ZF2001, Zhifei Biological, China) and adenovirus-vectored vaccine group (Ad5-nCoV, CanSino Biologics, China). The basic information of the enrolled volunteers is summarized in Table 1.