Initially, subunit vaccines were based on toxins purified from culture supernatants of host organisms. The increase in the use of genomics-based approaches to subunit vaccine development has facilitated the identification of several new candidates. This chapter reviews new systems, and focuses on plants that are being developed in an attempt to address several of the aforementioned concerns. The transgenic approach is used for producing proteins in growing plants and plant cell cultures via conventional fermentation. Another approach that is most frequently used with plant viruses is based on fusing known target peptide epitopes to the viral coat protein (CP) to obtain virus-like particles (VLPs) that mimic native viruses and present the epitopes on their surfaces, but are devoid of infectious genetic material. The launch vector technology lends itself to the creation of production modules with predetermined capacity, and by simply adding more modules, manufacturing capacity can be rapidly increased.