What is a vaccine passport and how might it be used? Yahoo News Explains

Many countries have indicated they are either considering or are already developing coronavirus vaccine passport systems for anyone wishing to travel. But what are these systems? And how might they be used? Yahoo News speaks to Amesh A. Adalja, senior scholar at Johns Hopkins Center for Health Security, and Nick Careen, senior vice president of airport, passenger, cargo and security of the International Air Transport Association (IATA) to find out.