Britain is starting to plan for a Covid-19 vaccine booster campaign starting later this year after top vaccine advisers said it might be necessary to give third shots to the elderly and most vulnerable from September.

The government said that a final decision on whether a vaccine booster campaign was needed had not been made, but officials had advised that preparations should begin on a precautionary basis.

The Joint Committee on Vaccination and Immunisation (JCVI) advised that there should be a plan to offer Covid-19 booster vaccines from September, starting with...