People are being urged to take part in important Covid-19 trials to determine if a third vaccine dose could protect against new variants of the virus.
The Cov-Boost study starts in June and needs to recruit 3,000 people of working age who had their first dose back when the vaccines were first rolled out in the U.K. in December or January.
The findings will help scientists determine if giving people a third jab in the autumn, similar to the flu vaccine programme, is needed to help combat further Covid-19 outbreaks.
Professor Saul Faust, chief investigator for the trial, said that it could help them to simply discover if some age groups need a booster, and others don't.
"The aim is to find out whether there should be a booster campaign and which vaccine to use," he explained.
The study will include doses of AstraZeneca, Pfizer and Moderna jabs, which have already been used on people as part of the ongoing vaccination rollout in the U.K.
People will also be given doses of vaccines from Novavax, Janssen, Valneva and CureVac, all of which are currently being trialled and have not yet been approved by the Medicines and Healthcare products Regulatory Agency (MHRA).
Participants will be asked to keep a diary of any potential side effects, but Faust explained that none of the vaccines will be "detrimental".
They will also have their blood tested to check for any levels of coronavirus antibodies.
The seven vaccines will be trialled at 18 sites across the country.