Making a vaccine against seasonal influenza is a constant catch-up game. Scientists must predict which of the constantly mutating virus strains will be most virulent six months in the future, the amount of time it takes to manufacture the vaccine. The system has worked well enough for the regular flu. But when new, virulent strains emerge–including the current, rapidly spreading swine flu (H1N1)–the traditional approach falls short. Even as consumers clamored for a vaccine, it took seven months and around 48,000 confirmed U.S. cases before the first H1N1 vaccines were shipped to hospitals around the country.