While the need for vaccines with the ability to generate an effective immune response has led to the combination of antigens with more than one adjuvant, the djuvant System approaches. The Adjuvant System approach aids in the development of vaccines that generate effective immune responses. In this study, the roles of three adjuvants, IFA, CpG and poly rRBD subunit Niraparib vaccination were investigated aimed at inducing an effective immune response through use of tailored adjuvant combinations and delivery routes. Consistent with above studies, all vaccination regimes containing rRBD induced an RBD-specific cellular and humoral immune response. However, a more robust immune response was elicited when mice were immunised with the RBD/A+C and RBD/I+C regimes. An unexpected result was the absence of neutralizing antibodies in the sera of RBD/I+C immunised mice, despite antiRBD specific IgG titres being similar for the RBD/I+C and RBD/ A+C regimes. To further understand the riddle, we detected the aantibody avidity of different vaccination regimes by aavidity ELISA. However, the results showed the high antibody avidity correlated with a high IgG titre in mice of RBD/I+C and RBD/ A+C groups. So, we speculated maybe the adjuvants of destroyed the conformation of rRBD and covered the antigen binding sites. Another probable cause of the low titer of neutralizing antibodies in the sera of RBD/I+C immunised mice was the delivery route of subcutaneous. As known, the subcutaneous may be associated with degradation at injection site, which leads to decreased bioavailability. Whatever, further studies are in process. Compared with other studies, the regimes in this study induced lower titres of neutralization antibodies. For example, the PI50 of alum plus CpG, the group showing the highest titer of neutralizing antibody in all immunization groups was 1:500. While the rRBD protein in the above studies acquired a 1:1000 in mice neutralization antibody titre. The differences may be caused by the detection methods of neutralization antibody. As showed in the materials and methods parts, the neutralization antibodies in this study were detected by a pseudovirus system which can be conducted in biosafety level-2 facilities. While the differences of induced neutralization antibodies among different groups can be shown clearly. The subclass of immunoglobulin induced after immunization is an indirect measure of the relative contribution of Th1-type cytokines vs. Th2-type cytokines. To characterise the immune response of the different vaccination regimes, IgG isotype including IgG1, IgG2a and IgG2b analyses were performed. As expected, the RBD/A regimes produced a Th2 response with high IgG1/IgG2 ratio. In contrast, mice received the RBD/A+C or RBD/I+C regimes revealed a Th1 skewed response. Consistently, the RBD/A+C or RBD/I+C regimes induced a systematic cellular immune response in mice by ELISpot analysis. The high level of IFN-c and IL-2 in the CBA was also a proof of the cellular immune response in mice. Besides, the mice in the RBD/A+C group had a high level of IL-4 and IL-10, which were an index of Th2 skewed response. Taken together, the RBD/A+C induced a Th1 and Th2 mixed immune responses, though the responses had a Th1 inclination.