Via The Torygraph, one that I am sure Leg-iron would have a lot of fun with (emphasis mine) :

The vaccine uses dummy virus cells grown in tobacco plants to immunise the body against the winter vomiting bug.

Rather than being injected, it is administered up the nose in the form of a powder and could offer protection from the virus for between six months and two years.

Norovirus is a highly contagious bug which is most potent at this time of year, causing diarrhoea, vomiting and flu-like symptoms which last for two to three days.

Because it is so easily transmissible from person to person, the virus is especially rife in hospitals and care homes as well as other crowded settings like schools, army barracks and cruise ships.

Although not normally dangerous, the condition can be deadly to very young and elderly patients.