When (and how) will we know if Omicron is taking over?

Over the next several months, the fight between Delta and Omicron is going to be scientifically fascinating.In the red corner is the current world champion Delta, which easily beat out every other variant of concern to date.In the blue corner is the challenger Omicron, whose continued existence probably relies on its ability to beat out the champion.But how will we know who's winning and when will we get a better sense of it all?Also on today's show:* What makes a virus go viral?* Who decides which variants you make vaccines for?* What happens if Omicron turns up in a place with no Delta (like Queensland or Tasmania, for example)?