"For many diseases, our immunological memories can endure like etchings in stone. Once children get shots for polio, they're usually protected for the rest of their lives. Unfortunately, the same can’t be said for the flu virus. When it comes to influenza, it’s as if we have short-term amnesia.
Every fall, doctors offices and pharmacies get a fresh load of influenza vaccines. Time and again, studies have demonstrated that flu vaccines are effective—but usually only for a single flu season. When the next flu season arrives, the viruses have changed, and we have little protection from the year before. We have to teach our immune systems yet another lesson."
Nice essay, from a master of the art of making science palatable to civilians. He very ably explores the concept of universal vaccines for flu - something I for one would welcome!