Can we create vaccines that mutate and spread?

Viruses mutate and spread from person to person, a dynamic process that often leaves us playing catch-up when there's a new disease outbreak. What if vaccines worked the same way? Virologist Leor Weinberger shares a scientific breakthrough: "hijacker therapy," a type of medical treatment that could attack, modify and spread alongside a virus, potentially treating afflicted individuals and slowing the spread of infections like HIV.