More than 7,000 people were hospitalised or died from Covid-19 in the UK during the summer of 2022 because they had not received the recommended number of vaccine doses, according to a study released Tuesday that was the first to cover Britain's entire population.

The researchers said the "landmark" population-wide study showed how important it is for people to keep getting booster jabs as Covid continues to pose a major health threat.

More than 90 percent of the UK's adult population were vaccinated during the earlier stages of the pandemic.

However, between June to September 2022, after the pandemic's emergency phase was declared over and attention turned elsewhere, around 44 percent of Britons were under-vaccinated, the researchers said.

Using individual health data from the National Health Service (NHS) as well as modelling, the researchers estimated that there would have been 7,180 fewer hospitalisations or deaths if everyone had been up to date with their shots.

That means that nearly 20 percent of the 40,000 Covid hospitalisations or deaths over the summer could have been avoided if Britons were fully vaccinated.

Cathie Sudlow, chief scientist at Health Data Research UK which led the research, told a press conference that the results clearly showed that "being fully and properly vaccinated is good for individuals and good across society."

- Taking the pulse of a nation -

The research, published in the Lancet journal, used secure, anonymised health data of everyone over the age of five across the UK's four nations.

The researchers said it was the first time such a study had included all 67 million people in Britain.

They called for the same approach to be deployed in other health research areas, such as cancer, diabetes and heart disease.

"We think this landmark study really sets a line in the sand to say this sort of thing is possible -- we need to be doing more of it," said Angela Wood, a co-author from the University of Cambridge.

The UK is uniquely suited to carry out such population-wide research because "virtually every interaction" with the NHS is recorded, said co-author Aziz Sheikh of the University of Edinburgh.

"There's nowhere else in the world that can do this," he added.

The under-vaccinated tended to be male, younger, non-white, from a more deprived background and have fewer existing health problems, the study said.

The recommended number of Covid vaccine doses has changed over time and varies between countries. The UK recommendation in June 2022 was one shot for those aged five-11, two for 12-15, three for 16-74 and four for people over 75.

Last week the World Health Organization warned that transmission of Covid increased in December, fuelled by gatherings over the Christmas holiday period. The JN.1 variant is now the most commonly reported around the globe.