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.