A vaccine is to be trialled on thousands of people to find out if it could protect against norovirus - a stomach bug that causes vomiting and diarrhoea. The easily spreadable winter virus can affect people of all ages and have huge consequences - often closing hospital wards, taking children out of school and keeping parents off work. The vaccine will be tested on around 25,000 adults, mostly over-60s, in more than six countries around the world over the next two years.

If successful, the researchers say it would reduce the number of vulnerable adults in hospital during winter, as well as the financial burden on health systems like the NHS. Vaccines against viruses like flu, Covid and RSV already exist and protect millions of people every year - but there has never been a vaccine licensed against norovirus . The vaccine being trialled is made by Moderna and is an mRNA vaccine.

Like the company's Covid jab, it delivers instructions to our immune systems on how to recognise an invasive virus and protect against it by producing antibodies. What's tricky about norovirus is that it's difficult to pin down. "There is a broad and shifting diversity of genotypes over time", says Dr Patrick Moore, a GP from Dorset, and chief investigator of the study.

So this vaccine contains three of the most common strains of the virus to get the best result possible. There are still many unknowns - for example, how long will protection from it last, how effective will it be and how often will the v.