Easy. We know EXACTLY what the genome is, it was mapped out over a year ago. That allows you target a specific part of the virus with a vaccine.

Having the map of the genome doesn't impart knowledge about how an epidemic plays out since that is heavily influenced by human behavior. Also once the bug infects someone, the course of the infection is variable depending their genetics, immune system, co-morbidities, strain, inoculum, whether they got a good night's sleep, etc. But it's pretty easy in the grand scheme to develop a very specific, targeted monkey wrench to stop the bug before it multiplies much.