THE world’s first clinical trial on a Covid-19 booster jab has launched in the UK.

Thousands of volunteers will get a booster jab as part of the trial.

Seven existing vaccines are to be tested in the Cov-Boost trial to see which jabs could be used in any forthcoming autumn vaccination programme.

Some 2,886 people aged 30 and older are being recruited at 18 NHS sites from London to Glasgow, with the first booster jabs administered in early June.

Scientists want people who received their first dose of either Pfizer/BioNTech or AstraZeneca in December or January to sign up, and hope people aged 75 and over will also come forward.

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Experts believe that all seven vaccines will boost immunity, and lab studies will check their response to variants circulating in the UK, including those from India, Kent and South Africa.

The £19.3 million clinical trial will test the Pfizer jab alongside those from AstraZeneca, Moderna, Novavax, Janssen from Johnson & Johnson, Valneva and CureVac.

Three of the vaccines will also be tested at a half dose, with experts expecting an adequate immune response at this level.

The half doses will inform whether side-effects are reduced at a lower dose, and could offer useful information to countries where vaccine supply may be more scarce.

The 18 NHS sites across the UK will be split into three groups, with each group testing a different set of vaccines.

The 18 sites include Southampton, London, Leicester, Bournemouth, Portsmouth, Wrexham, Bradford, Oxford, Glasgow, Leeds, Cambridge, Birmingham, Brighton, Stockport, Liverpool and Exeter.

England's health and social care secretary Matt Hancock said: “The UK vaccination programme has been a phenomenal national effort, with seven in 10 UK adults now having had their first Covid-19 jab.

Professor Saul Faust, director of the National Institute for Health Research Southampton clinical research facility and lead investigator for the trial, said the “hope of a booster is that we raise the antibody level enough to be able to cover existing and variant strains of coronavirus.”

He added: “We’re hoping the immune responses will be high enough to protect people against all the strains circulating in the UK, including we’ll be testing in the lab against the Indian variant, the South African variant, the Kent variant as well as the original strain.”

Vaccines minister Nadhim Zahawi said: “Having taken part in a Covid-19 vaccine clinical trial myself, I would encourage everyone eligible to volunteer – whatever your religion, ethnicity or background.”

“It’s a fantastic opportunity to get involved with such an historic initiative.”