Mario Pezotti at Verona University in Italy says that Arntzen's work "demonstrates that you can easily speed up the production systems for any vaccine and especially for viruses that change quickly."

The second main challenge for making plant-based vaccines has been to develop a final product that meets pharmaceutical standards, says Carole Cramer, executive director of the Arkansas Biosciences Institute at Arkansas State University in Jonesboro. The aim of earlier research was to produce edible vaccines that would allow cheap and safe delivery in developing countries where facilities for storing purified protein jabs that need to be cooled are limited.

Although transgenic potatoes, tomatoes or rice can produce functioning vaccine molecules, including those that are effective against the norovirus, "not having completely controlled doses has been a challenge, especially in Western medicine," says Cane. "Any viable product will have to be completely purified and precisely deliverable--for example, as a nose spray," she says.

Tobacco's high biomass production in combination with affordable extraction technologies adapted from the food industry makes Arntzen confident that the norovirus vaccine can be produced at very low costs. He anticipates that clinical trials will start in early 2010.

"The current concern about swine flu demonstrates that the world needs vaccines at high speed and low costs, and this is where plant-based products like this norovirus vaccine have high potential," says Pezotti.

Yuri Gleba of Nomad Bioscience in Munich, Germany, who first developed the three-step plant infection system used for the norovirus project, has tested it on more than 50 pharmaceutically- relevant proteins. Gleba believes the approach could become an effective tool anywhere where fast-response production of proteins is required.

"When it comes to bioterrorism, for example, such a plant-based system could be used to cheaply grow compounds in anticipation of a problem, [saving] only the most expensive final processing steps for the case of an emergency."