UK begins 'booster' shot trial of 7 different COVID-19 vaccines

LONDON - Britain launched a nationwide study on Wednesday to explore whether giving a third dose "booster" shot of coronavirus vaccines would be safe and effective in extending immune protection against COVID-19.

The trial, which aims to recruit nearly 3,000 participants, will look at seven different COVID-19 shots, some of which are already approved by regulators and in wide use and others that are still in development. British officials have been planning for the possibility of a booster vaccination campaign before the winter after initially targeting immunisation with a two-dose schedule for the whole adult population by the summer.