Viruses multiply incredibly quickly once they've infected their victim–so fast that antiviral medications such as Tamiflu are only effective if given during the first few days of an infection. After that, the viral load is just too high for a single drug to fight off. But researchers are working on a treatment for the H1N1 virus (or swine flu) that uses a different approach. Rather than disabling the virus with a drug, they're creating a vaccine that can activate and steer a patient's own immune cells to attack the invader

via Technology Review: Arming the Immune System against H1N1.