One possible solution is the development of oral vaccines. This proved to be a great advantage in the treatment of polio. Unlike injectable vaccines, "they can activate the mucosal immune system against many pathogens by oral delivery" and also because they do not contain whole pathogens, there is no risk of actually transmitting the disease by accident through the vaccination process (Kumar et al. 2002: 86). Plant-based vaccines have proven to be particularly effective in the developing world through the use of transgenic banana plants. At present, the surface antigen of Hepatitis B (HBsAg) has been successfully found to be expressed in transgenic tobacco plants as well. "The HBsAg derived from transgenic tobacco plants is physically, biochemically and immunologically similar to yeast derived rHBsAg" but is cheaper to produce (Kumar et al. 2002: 87). Both transgenic tobacco and banana plants, it is hoped, hold the potential to develop an effective oral vaccine.
The series of experiments conducted by the study's authors to support their exploratory research to find plant-based vaccines were promising. For the transgenic tobacco plants, "Western analysis confirmed the presence of HBsAg specific band corresponding to yeast derived rHBsAg in pHBs100 and pHER100 transformed tobacco cells whereas in the control non-transformed cells the same was absent…the denatured HBsAg expressed in plant cells showed 4 kDa peptides similar to yeast derived rHBsAg" (Kumar et al. 2002: 91). This antigen is not naturally occurring in tobacco plants, it should be noted: transgenic manipulation would be required for the vaccine to be generated, thus there still would be considerable expense in generating the vaccine initially. The hope would be, however, that once it was developed, it would be useful in the context of the developing world to provide treatment.
The most desirable and promising potential vaccine source, however, would still be to derive the vaccine from a banana plant, given the proliferation of the fruit in the tropics and also its palatability. "Expression of HBsAg in bananas may be advantageous as they are grown in most of the tropical and subtropical countries, where cost effective vaccines are required and their digestibility and palatability by infants makes it an attractive choice" (Kumar et al. 2002: 93). It must be noted that the development of the vaccine in any plant form is still very much in its nascent stages. At present, the closest to an oral vaccine that has been derived in a lab is an HBsAg prototype from a transgenic potato plant tested in mice. Still, the research indicates potentially promising developments in this area which should not be ignored.