As the Delta variant rages across the United States, hospitals are filling up with unvaccinated patients. Americans are suffering and dying needlessly, because the country has enough doses to vaccinate every eligible person. But the pathogen has allies: right-wing fanatics on cable TV who sow mistrust in life-saving inoculations, social media charlatans pushing quack cures, and plain old stubbornness, laziness, ignorance, or complacency among the citizenry. Historian John Barry, author of 'The Great Influenza: The Story of the Deadliest Pandemic in History,' returns to the podcast to talk about Delta and the variants to come, the politics of pandemics, and reasons to be optimistic. Yes, optimistic!