LONDON – The U.K. is launching a trial to investigate the potential use of seven different COVID-19 vaccines as boosters, to provide safety and immunogenicity data for if/when immune responses to initial vaccination wane and a revaccination campaign is needed later in the year. The trial, at 18 sites across the country, will recruit 2,886 participants who previously received two doses of either Astrazeneca plc or Pfizer Inc./Biontech SE’s COVID-19 vaccines.