Author contributions
N.A.K. acted as the principal investigator of the trial. N.A.K., Q.M.L., Y.T.Z., X.M.Y., Y.K.Y., JingZ.(NVSI) and Y.K. conceived the study and designed the trial protocol. Q.M.L., JingZ.(NVSI), Y.L. and J.G.S. were the designers of the vaccine NVSI-06-09. Q.M.L., Y.T.Z., and X.M.Y. supervised the project. X.F.Z., Y.Q.J., H.Z., Z.M.L., Y.N.H., J.W.H., S.C., Z.J.M., X.J.G. and X.Y.M. contributed to the production of NVSI-06-09 vaccine. H.W. and JinZ. were the providers of the inactivated vaccine BBIBP-CorV. X.M.Y., Y.T.Z., I.E., and Y.K.Y. participated in the organization and management of the project. T.Y., Y.K., M.L., L.Q., W.Z., P.X., X.Zhang, C.Q., D.Y.L., and S.S.Y. contributed to the implementation of the project. H.M.M., Z.N.W., and J.L.Y. were responsible for sample collection and processing. G.W., K.X., W.L., JingZ.(CDC), M.Y. and S.M. performed the laboratory tests of the serum samples. G.W., K.X., Y.L., N.L., X.Zheng, F.J.S., Z.B.H., F.T., F.Z., J.J.W., X.Y.L., X.L., L.F.D., and Z.H.L. contributed to the development and validation of serum testing method and also participated in paper preparation. S.H. and M.S.E. gathered and processed the trial data. Z.J., X.C., and Y.T. were responsible for statistical analysis of the clinical data. Q.M.L., JingZ.(NVSI), Y.L., G.W., Y.K.Y., and K.X. analyzed and interpreted the trial results. J.G.S., Y.L., JingZ.(NVSI), K.X., L.F.D., S.S., and S.S.Y. drafted the manuscript. Q.M.L. and G.W. revised the manuscript. All authors approved the final manuscript. The corresponding authors are responsible for the decision to submit the manuscript.