Name a recombinant vaccine that is currently being used in a vaccination program.

(N/A) The Hepatitis $B$ recombinant vaccine (e.g.,Engerix-$B$) is a widely used vaccine produced using recombinant $DNA$ technology. It is prepared by inserting the gene encoding the Hepatitis $B$ surface antigen $(HBsAg)$ into yeast cells,which then produce the antigen. This antigen is purified and used as a vaccine to induce an immune response against the Hepatitis $B$ virus.