Minnesota Health Department officials say there's plenty of vaccine to go around this influenza season. But having flu vaccine available and preventing the spread of the flu are two different things. Many people still need convincing to undergo innoculation. Dr. Jon Hallberg is the medical director of the University of Minnesota Primary Care Center and our regular medical analyst. He says the flu virus kills nearly 36,000 Americans each year and infects up to 20 percent of the US population.