BERLIN (Reuters Health) - German scientists have grown genetically modified carrots that contain the vaccine against hepatitis B, which they say could dramatically cut the costs of preventing the disease.

Development has reached the stage where the carrots are ready to begin pre-clinical trials and researchers say that carrot-sourced vaccines could be a reality within about 3 years.

The current vaccine against hepatitis B is expensive to produce and is administered via three injections, which further increases costs and strains health services.

But now plant specialists and virologists from Giessen University in Germany have successfully inserted the gene for the hepatitis B surface antigen normally used in the vaccine into carrots, and have been growing the vegetables in the thousands.

"We can make 100,000 or so plants in 2 weeks and within 3 months they are ready to eat," said Dr. Jafargholi Imani from the research group at Giessen University.

He explained to Reuters Health that carrots are particularly good for this purpose as they are easy to grow in many different climates and soil types.

"But it's not as if we will be able to hand out packets of seeds for people to grow their own," he said. "These are transgenic plants and need to be isolated. But it does mean that the plants can be grown where the vaccine is needed."

Carrots are also easy to store, transport and consume raw, he said. Other attempts to grow transgenic drug-containing tomatoes or potatoes have suffered from the delicate physical nature of tomatoes and the fact that potatoes are difficult to eat raw, while cooking would destroy the vaccine.

Imani's team has been working on the carrots for around 2 years now and are about to publish their initial report in the Dutch journal Plant Cell, Tissue and Organ Culture. The paper has already been accepted and should appear this summer.

"This now needs to be tested clinically, on animals and then people, to see what kind of dosage will be needed and how it all works in practice," he said, adding that such testing would likely take at least 2 years.

"Here we could be ready to start producing within months if all goes according to plan. I am very optimistic; it has been working very well. At the moment the vaccine costs up to 200 euros and you have to have three injections. We can afford this in the developed world but in other places it is not an option."

Giessen University estimates there are around 350 million people around the world infected with hepatitis B virus, which can severely damage the liver and can be fatal. One million people are believed to die from the disease annually.