Speaking at the first government Covid briefing of the year, the prime minister said it was likely many countries would seek evidence of booster jabs.
Johnson’s comments came as the government continued to resist pressure to impose further Covid restrictions in England to guard against additional cases of the new Omicron variant.
Scotland and Wales have toughened their Covid measures in an attempt to mitigate the Omicron wave.
Addressing the press and public at Downing Street on Tuesday (4 December), Johnson urged those already fully vaccinated to get their boosters, and those yet to receive any vaccine doses to come forward and get jabbed.
