Recombinant DNA vaccines are composed of a small circular DNA (plasmid) that has very small fragment of pathogen DNA incorporated in it so as to produce one or more specific proteins of the pathogen.
This recombinant DNA is again introduced in to the bacterial or yeast cells, where it uses cell's machinery to produce polypeptides of pathogen. These are then used as vaccine to trigger variety of immune responses.
Vaccines produced by using this approach allow production in large scale as:
(i) Bird flu DNA vaccine.
(ii) Hepatitis-B vaccine produced from yeast.
The Advantages include :
(i) Recombinant DNA vaccines are advantageous over killed or attenuated vaccines since they do not get mutated or virulent again which is seen in case of attenuated vaccine.
(ii) These are highly pure, specific and elicit strong immune response.