Plant-derived vaccines

Vaccines are the most cost-effective and efficacious means of reducing the disease burden of infectious diseases. Novel approaches to improve product quality and improve access while lowering production costs are continuously being sought. Traditionally vaccines are prepared by using an attenuated version of the pathogen or by preparing and inactivating a disease-causing organism or a suitable part of it, e.g. a toxin, and administering it in quantities sufficient to induce immunity. Such vaccines have the unavoidable potential for contamination with adventitious agents that can infect such materials. A new and exciting possibility is the production of vaccine antigens in genetically modified plants which can then be extracted and purified by conventional methods. Such vaccines could either be eaten or applied to mucosal surfaces.

Plant-derived vaccines have several advantages. They can be produced cheaply in very high amounts, carrier plants such as potatoes and corn are readily accepted by patients and antigens derived from them are stable and can be stored for long periods of time. The likelihood that contamination by a plant virus would have an adverse effect on humans is almost negligible. There are several technical challenges concerning plant-derived vaccines that must be resolved before they can enter wide-scale use and the regulatory requirements for this novel class of vaccines must be established. In addition, public acceptance of the new technology must be ensured. As the development of plant-derived vaccines matures, WHO will continue to serve as a forum for the international harmonization of requirements.