What is *cough* the Flu Shot Anyway?

Last week my wife and I both got sick.  We both passed the opportunity to get flu shots.  Would it help?  What magic elixir can keep someone from being sick?  How does it all work?

The flu, or influenza, is a virus, which Matt described very well in his post Viruses - A Vector to Remember. This particular virus is one bad hombre.  What makes this virus so bad is that the DNA that it carries makes people sick, sometimes very sick.  In fact, during World War I a flu epidemic known as the Spanish Flu infected half a billion people and may have killed as much as 3% of the world's population.

The Spanish Flu was not the first virus to leave a big wake of destruction.  Toward the end of the 1700s, smallpox killed nearly half a billion people in Europe alone.  While you are likely to catch the flu in your life, you will not get smallpox, thanks to the smallpox vaccine.



You can think of the human immune system like a town from the wild west.  The viruses that cause smallpox and the flu are outlaws, banned from town.  The vaccines are like wanted posters, showing your immune cells, the sheriff and deputies, what the bad guys look like.  The sheriff and deputies will know exactly what to look for if they've seen a wanted poster without ever needing to see the outlaws in person.  When the outlaws come to town they are immediately recognized and arrested.  In the same way, vaccines show your immune cells what to look for so that they can immediately tag the viruses for destruction.

Vaccines are usually made of weakened, disabled, or partly-assembled viruses so that the body can learn to recognize them without actually getting sick.  Because they can have some mild effect, standard vaccines are not recommended for babies or elderly people who have weaker immune systems.  Before flu season each year, a team at the World Health Organization (WHO) does their best to predict what the newest mutations of the flu virus will look like this year.  Vaccine companies can use these predictions to make vaccines that can alert your immune system to a few of the most common viruses.

Next year, I plan to give my immune system a good heads up with a quick stop at CVS for my flu shot.

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