A team of Japanese researchers has developed a type of rice that can carry a vaccine for cholera, a step that could one day ease delivery of vaccines in developing countries.

While it's only the latest of several plants being tested as potential means of producing vaccines, the development is potentially important in medically underserved countries that lack refrigeration to store regular vaccines.

But the work is preliminary, having been tested only in mice.

That means the new vaccine could have an advantage against pathogens that typically infect these membranes, such as cholera, E. coli, human immunodeficiency virus, influenza virus and the SARS virus.

"This has not progressed to the degree that we had hoped it would by this time,"

Mason cautioned that getting a good response to orally delivered material can be tricky in the harsh environment of the digestive system.