A specific synthetic antigenic peptide that contains a sequence of about 20 amino acid residues corresponding to a certain region of the antigenic Picornavirus capsid protein such as the VPl capsids of foot-and-mouth disease and poliomyelitis viruses. That region is located at a distance of about 60 to about 75 percent of the total amino acid length measured from the amino-terminus. Specific synthetic peptide-containing vaccines that produce antibodies that protect animal hosts from the Picornaviruses, as well as antibodies to and diagnostics for Picornavirus antigens are disclosed.