The flu is going to be brutal this year. The Centers for Disease Control and Prevention is already seeing more cases than usual, and we've yet to hit peak flu season. To make matters worse, this year's flu vaccine is less effective than usual, thanks to decisions that were made nearly a year ago. Making the flu vaccine is like predicting the future, and predicting the future is hard. Flu vaccine production is a slow, old-fashioned process of growing viruses in chicken eggs. It hasn't changed much since 1940s. That's why flu vaccines have to be formulated months beforehand, and that's why the flu vaccine is less effective than usual this year. It's still worth getting a shot, especially if you're young, elderly, or otherwise immune-compromised; this year's dose protects against three out of the four strains it's targeting. But there's no guarantee it'll work, which is why we're seeing this: The reason influenza is so widespread this year comes down to the complexities of getting the flu vaccine just right. It involves a hundred million chicken eggs, and a dose of luck. Flu Prognostication Next month—while many of us are wheezing our way through this flu season—the making of next year's flu vaccine will begin. Each February, the World Health Organization identifies the three or four strains to include in the vaccine for the next year's onslaught. More details via Gizmodo.