ProVacs
New and improved vaccines are urgently needed to address the global scourge of infectious diseases. Yet
the development and introduction of new vaccines faces many challenges. The ProVacs initiative at the Biodesign Institute is taking up this challenge and is responding to the need for new types of vaccines produced in plants.
Several characteristics make plant-derived vaccines particularly attractive for controlling infectious diseases globally and specifically in developing countries:
- They could be produced on a very large scale and at very low cost, perhaps as little as a few cents per dose.
- They could be orally active, eliminating the need for injection and the associated cost and safety concerns.
- Developing countries could launch and carry forward their development and ultimately their production.
- They evoke mucosal immunity, thus able to address diseases such as AIDS.
- They should be heat stable, largely eliminating the need for a cold chain for these vaccines.
- Multi-antigen vaccines should be possible, either by multiple gene splicing or by mixing various plant-derived vaccines.
- They may have the added advantage of being safer because they won't include animal-related contaminants from the manufacturing process.
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Blueprint for Production of Plant-derived Vaccines Vaccine: Volume 23, Issue 15, Pages 1753-1885 (7 March 2005) Plant-derived vaccines: Cost of Production Plant-derived vaccines: Regulatory issues Presentations from November 2002 Meeting Presentations from January 2005 Meeting
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Most vaccines today are made in insect or mammalian cell cultures or tissues, fertilized eggs, or bacterial or yeast fermentation systems and then purified. These vaccines usually need to be refrigerated from the time they are made, through transport, until used. This adds significant cost to vaccination programs, and, in some circumstances in developing countries, makes it difficult to get vaccines to remote or hard-to-access places. Dried plant extracts containing subunit vaccines offer new solutions and opportunities.
A recent scientific Blueprint by the Biodesign Institute, based on a series of international consultations, demonstrates that the development of plant-derived vaccines is both straightforward and achievable.
Other ongoing work on regulatory issues led to a consultation meeting at WHO. Leading experts from around the world were present and the meeting concluded that existing guidelines for the development, evaluation, and use of vaccines made by traditional methods can be applied to plant-derived vaccines. For plant-derived vaccines some specific issues will have to be addressed. These are discussed in detail in a publication on regulatory issues (published by Vaccine).
Another project evaluated the cost of producing plant-derived vaccines. This study includes a number of variables, including the type of plant used, the scale of production, the country of production (developed vs. developing countries), whether the resulting product is taken orally or injected, and the method of final product preparation. Using plants as a production system, instead of cell culture, eggs, or fermentation systems, is expected to be much more cost effective. For example, our calculations indicate that the range of cost of goods per dose of a hepatitis B vaccine antigen is between $0.04 and $0.10. Once packaged, the total cost per finished dose of could be as low as $0.06 produced in the United States, and $0.03 if produced in India (the current lowest price for hepatitis B vaccine in a 10 dose vial is $0.27). We have also computed the “effective cost,” i.e. the cost per dose to deliver in a developing country immunization program and the percent savings that could be enjoyed over the effective cost using plant-derived vaccines. The results are even more compelling: The effective cost of yeast derived hepatitis B vaccine delivered in a 10 dose vial is estimated at $0.42; plant-derived and administered orally is around $0.04 which represents up to a 90% savings. The report on the cost of production concludes that enough hepatitis B antigen to immunize all babies in the world each year could be grown on less than 200 acres. All the hepatitis B vaccine required annually for China could be produced on a 40-acre plot.
The production in plants of large quantities of vaccines for oral administration is poised to revolutionize the world of vaccination and help bring to the poor the promise of existing and new vaccines for controlling infectious diseases. Due to economic and market realities, this promise will be achieved only through the collaboration of the public and private sectors with significant investments by both parties. These investments however will yield rich dividends in the form of widely available, inexpensive, orally administered, heat stable vaccines.
