Sequential immunization is one of the special means to solve the shortage of vaccines, respond to SARS-CoV-2 variants and improve the efficacy of vaccines in the current pandemic period. This article mainly reviewed five sequential immunization strategies using the vaccines authorized by World Health Organization: priming with inactivated vaccine and boosting with recombinant protein vaccine, vector vaccine or mRNA vaccine; priming with vector vaccine and boosting with mRNA vaccine; prime-boost immunization with mRNA vaccines produced by different manufactures. Results of the related studies showed that heterologous sequential immunization strategies were safe and effective, and higher immunogenicity and efficacy could be achieved by sequential immunization. In addition, sequential immunization could provide certain protective effects against SARS-CoV-2 variants.