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

A recombinant vaccine is a vaccine produced through recombinant $DNA$ technology.

This involves inserting the $DNA$ encoding an antigen that stimulates an immune response into bacterial or mammalian cells.

Recombinant $DNA$  technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast.

Vaccines produced using this approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis $\mathrm{B}$ vaccine (Recombivax $HB$) produced from yeast.

As of June $2015$ one human $DNA$ vaccine had been approved for human use, the single-dose Japanese encephalitis vaccine called $IMOJEV$, released in $2010$ in Australia.

Advantages of recombinant $DNA$ vaccines :

$(1)$ There is no risk for infection. $(2)$ Ease of development and production. $(3)$ There is Stability for storage and shipping. $(4)$ It is Cost-effective. $(5)$ Expression and purification of recombinant proteins is observed. (6) Long-term persistence of immunogen is present in them. $(7)$ In vivo expression ensures protein more closely resembles normal eukaryotic structure, with accompanying post-translational modifications.