Boris Johnson suggested on Wednesday that some pubs might require customers to produce COVID-19 vaccine certificates, an idea that he had previously deemed unlikely.Almost 29 million people have received their first vaccine dose in Britain already in the fastest rollout in Europe, and there have been calls to open up the economy faster because of the success of the vaccination programme.Appearing before a committee of senior lawmakers, Johnson said the “basic concept of a vaccine certification should not be totally alien to us”, citing how surgeons were required to have a Hepatitis B shot.