What happens after genetically modified plasmids are inserted into bacteria?

The answer to the question is: Once a new DNA is inserted, the modified plasmid can be grown in bacteria for self-replication to make endless copies.
>The plasmid is genetically modified to produce 1 or 2 specific proteins from a pathogen and then purified for immunization.

>A plasmids are small double-stranded unit of DNA.They are  usually circular but sometimes linear, that exists independent of the chromosome and is capable of self-replication. Each plasmid carries only a few genes.

The specialisation of cells is paramount to having a functional multicellular organism. if the body didn't specialise then it wouldn't be an organism; it would just be a colony of cells much like those that bacteria and other single celled organisms form.