Study the article Is The Time Coming for Plant-Made Vaccines? @ http://www.scitechnol.com/infectious-diseases-immunological-techniques.php.
The following article can be summarized as:
Vaccines have significantly improved human health since their introduction in the last century. They are the most potential weapons to fight the majority of infectious diseases, which are responsible of more than 45% of the total deaths in developing countries. Traditional vaccines are made of a live attenuated or killed pathogen, and either injected or given orally. There are other two categories of vaccines, subunit vaccines and nucleic acid vaccines, being the choice of producing one of them related to factors such as pathogenesis, immunobiology, and epidemiology of the disease.