The invention relates to genetically modified plants and progeny thereof which constitute edible plant-derived mucosal vaccines and injectable plant-derived mucosal vaccines against Severe Acute Respiratory Syndrome (SARS). The invention relates to a recombinant vector that transforms specifically, but not limited to, the nuclei and/or plastids of tobacco, tomato and lettuce plants for antigen production. In specific embodiments, the plastid transformation vector expressing the nucleotide sequences are pCV1, pCV6 and pCV8, and their derivatives containing an S1 with nucleotide (but not amino acid) changes to optimize codon usage for expression in plants. The present invention relates to methods of making the modified plants which comprises transformation of plants with vectors for nuclear expression and/or plastid expression of nucleotide sequences of the SARS-CoV virus, fragments, derivatives, analogs, or variants thereof. The present invention also relates to methods of immunization against SARS and methods of antibody detection using the SARS-CoV antigens generated by the plastid and/or nuclear vector(s) transformed plants.