What are recombinant DNA vaccines?

What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.

Recombinant DNA vaccines are made up of a small circular DNA (plasmid) that has very tiny piece of pathogen DNA incorporated in it to produce one or two specific proteins of the pathogen.
This recombinant DNA is introduced into the bacteria or yeast cells, where it can use cell’s machinery to produce polypeptides of pathogen.
These are used as vaccines to trigger a range of immune responses. Vaccines produced by using this approach allow large scale production, e.g.
(i) Hepatitis-B vaccine produced from yeast.
(ii) Bird flu DNA vaccine.
(i) Recombinant DNA vaccines are advantageous over killed or attenuated vaccines since, they do not get virulent or mutated again as it is seen in case of attenuated vaccines.
(ii) Secondly these are highly pure, specific and elicit strong immune response.