Mulesky et al. [100] pointed out two reasons that make using crops to produce drugs interesting for industry. These are (i) crops can be employed more efficiently in this process than animals or bacteria, with a larger output achieved with fewer resources, and (ii) the oral delivery of the drugs produced to people and animals is easier. A third reason is the high-level production of antigens for use as vaccines and their tests for immunological efficacy in animal studies [3] . The hyper-expression of vaccine antigens or therapeutic proteins in transgenic chloroplasts (leaves) or chromoplasts (fruits/roots) and antibiotic-free selection systems available in plastid transformation systems made possible the oral delivery of vaccine antigens against cholera, tetanus, anthrax, plague, and canine parvovirus, [101] [102] [103] [104] and reviews of [102, 105, 3 and 106] explained why plastid engineering can be regarded as an attractive strategy and environmentally friendly approach for the production of vaccines, therapeutic proteins, and biomaterials, and provided some examples. Kumar & Daniell [107] described various techniques for creating plastid transgenic plants and their biochemical and molecular characterization. They also provided suitable examples for application of chloroplast genetic engineering in human medicine.