Scientists say they are ready to begin human testing of a plant-based vaccine¹ for the winter vomiting² virus.

科学家称他们准备进行对付冬天呕吐病毒的植物提取疫苗的人体试验。

Outbreaks have happen onboard cruise ships

The norovirus stomach bug³ is highly contagious⁴（传染性的，会传播的） and can rapidly sweep through 'close-knit' environments like hospitals, schools and cruise ships（游艇）.

Currently there is no vaccine to prevent the million cases that occur each year in the UK alone.

The latest US work from Arizona State University was presented to a meeting of the American Chemical Society.

A number of research teams have been looking at developing a norovirus vaccine.

But because noroviruses are continually mutating, much like flu, it is a moving target for vaccine developers and production costs can skyrocket.

According to the Arizona team, using plants to make and grow the vaccines⁵ offers an answer to this because the manufacturing process is fast enough to keep pace with the shape-shifting virus.

Lead researcher Dr Charles Arntzen said: "With plant-based vaccines, we can generate the first gram quantities of the drug and do clinical tests within eight to 10 weeks.

"We could easily scale that up for commercial use in a two- to four-month period."

There are cost advantages too relating to vaccine purification and formulation, says Dr Arntzen.

After successful experiments in mice of a candidate vaccine, his team has developed a nasal delivery system for the vaccine that is ready for testing in clinical trials planned for later this year.

The new vaccine was manufactured in a tobacco plant using an engineered plant virus. It contains none of the infectious material of the original virus but is able to trigger the body's immune response to ward⁶ off an actual norovirus infection.

A spokeswoman for the Health Protection Agency said: "There are several vaccines for norovirus in development but all are probably several years away from being in general use.

"In the meantime, until one is produced that is effective and safe we recommend strict adherence⁷（附著，固守） to the outbreak control measures that exist to stop the virus spreading in hospitals and cruise ships.

"On an individual level, if someone has a norovirus infection they are advised to stay at home and practise good hand hygiene⁸（卫生） using soap and water to stop the virus from spreading to other members of the household."