Every now and then, it happens. You take the time to get a flu shot, but you wind up sick anyway. Bummer. That's the problem with the flu, it's not just one virus -- it's multiple variant strains. Every year, researchers have to choose one common strain on which to base the season's new vaccine. One day, that kind of guesswork could be a thing of the past: according to a new studies in Nature Medicine and Science, researchers are making significant progress on vaccines that fight multiple flu strains simultaneously.