The protective efficacies of current licensed vaccines against?COVID-19 have significantly reduced as a result of SARS-CoV-2 variants of concern?(VOCs) which carried multiple mutations in the Spike (S) protein. Considering that?these vaccines were developed based on the S protein of the original SARS-CoV-2?Wuhan strain, we designed a recombinant plasmid DNA vaccine based on highly?conserved and immunogenic B and T cell epitopes against SARS-CoV-2 Wuhan strain?and the Omicron VOC. Literature mining and bioinformatics were used to?identify 6 immunogenic peptides from conserved regions of the SARS-CoV-2 S and?membrane (M) proteins. Nucleotide sequences encoding these peptides representing?highly conserved B and T cell epitopes were cloned into a pVAX1 vector to form the?pVAX1/S2-6EHGFP recombinant DNA plasmid vaccine. The DNA vaccine was?intranasally or intramuscularly administered to BALB/c mice and evaluations of?humoral and cellular immune responses were performed. The intramuscular?administration of pVAX1/S2-6EHGFP was associated with a significantly higher?percentage of CD8 T cells expressing IFN-γ when compared with the empty vector?and PBS controls. Intramuscular or intranasal administrations of pVAX1/S2-6EHGFP?resulted in robust IgG antibody responses. Sera from mice intramuscularly immunized?with pVAX1/S2-6EHGFP were found to elicit neutralizing antibodies capable of?SARS-CoV-2 Omicron variant with the ACE2 cell surface receptor. This study?demonstrated that the DNA vaccine construct encoding highly conserved immunogenic?B and T cell epitopes was capable of eliciting potent humoral and cellular immune?responses in mice.