A team of researchers led by Hania El-itriby, director of Cairo's Agricultural Genetic Engineering Research Institute, developed GM maize plants that produce the protein known as HbsAg, which elicits an immune response against the hepatitis B virus and could be used as a vaccine.

The scientists are now attempting to increase the amount of the protein produced by the plants. They have not yet tested the effectiveness of the edible vaccine in animals and humans, but expect that tests will start early next year.

Reporting the results at an international conference on genetic engineering and biotechnology in Cairo last month, El-itriby said that producing a cheap, effective vaccine against the disease is vital, as many people are excluded from immunisation programmes because of the expense of the vaccines.

She added that her team's research is a step towards a cheap, edible vaccine for developing countries that would not require refrigerators for storage, or skilled medical personnel and needles to deliver the vaccine.