Why Get a Flu Shot Every Year?

Q. Can you tell us about flu vaccinations? I don’t understand how the vaccine can wear off so quickly that it’s required every year. What other vaccine acts like this?
How can we be so confident in guessing which viruses will be prevalent in the coming season? I keep wondering if the vaccine really makes sense, since I doubt that many people actually die from flu.
A. Flu viruses evolve quickly, which is why each year the vaccine is made to protect against different strains. If you catch the flu, your body will recognize that particular strain, but not the slightly different one that may emerge next year or the year after.
You are right that most other vaccines work for much longer than a flu vaccine. Those organisms do not mutate as rapidly as influenza viruses.
Because virologists have to predict which flu strains will become a problem many months ahead of time, they don’t always guess correctly. Nonetheless, the flu vaccine saves lives. Experts estimate that over the last three decades anywhere from 3,000 to 49,000 people die annually from complications of influenza.