Call me Immunity. My friends call me “Private I,” because that’s what I do—I’m a private investigator, a detective, a shamus. I track down criminals and make sure they don’t get away with any funny business. Take this one case. Now I know there are a whole lot of bad girls in the city, but this one floozy—let’s call her “Flu” for short—she was a real piece of work.
I wasn’t prepared for Flu the first time we met. I ran into her at what I like to call my “second office,” a half-legal seedy little nightclub joint down by the docks. She was leaning on the piano, pretending to sing the blues. One look at her figure and long blonde hair and you knew she hadn’t been hired for her singing voice. We got acquainted. Matters got real friendly; I was too distracted to notice the three tough guys sitting in the corner. Next thing I know, I’m waking up in the gutter, no wallet, high fever, a pounding headache and a throat that feels like I’ve been gargling broken glass. Damn Flu.
A year rolls by and I find myself back at that that old divey club. I see the new girl—dark hair and a red dress that leaves nothing to the imagination. We get cozy—a couple of drinks and bang! Next day I’m back in the gutter feeling about as fresh as a day old cigarette butt. I realize my mistake too late. Flu again. She’d been around the block, been associating with some new people; a little hair dye and plastic surgery and I hadn’t even recognized her.
Months pass. I hire an assistant, a tough guy we call Max the Vacc. We call him that because his real name, Maximilian Vaccination is just too many damn syllables after a few whiskeys. Anyway, good old Max the Vacc tells me about this little system he’s got all worked out. He keeps photos of all the known floozies who work the bars. Some of them are old photos, and some are wearing wigs, but he’s got most of the likely characters in his collection. We go down to my “second office” to try out the system. The new gal at the bar looked just like one of the bad girls from Max the Vacc’s mug shots, so when she came over to our table all cute-like, trying to sit on my knee—I was prepared. I had all my defenses ready. “Immunity,” I said to myself, “this Vaccination guy—I think this might be the beginning of a beautiful friendship.”
Dashiell Hammett is probably rolling over in his grave right about now, but rhetorical flourishes aside, it’s basically how the flu vaccine works. Every year, the most common flu virus is slightly different. Like a promiscuous floozy who “gets around” one human flu virus will associate with many human flu viruses and exchange genetic material. This gradual process is called antigenic drift. Flu viruses are especially well-adapted for this process because the flu virus is segmented (think a string of beads) and thus can easily re-assort the individual viral segments. (Think of cutting up two strings of beads and mixing them together—you could easily restring a new necklace from a mixture of beads from the two original necklaces.)
Antigenic drift is one of the reasons that scientists have to cook up a new flu vaccine each year. They need to approximate what the new flu of the year is going to look like, although (like Max the Vacc with his slightly outdated mug shots) sometimes they can’t predict exactly what the most prevalent virus will be. Consequently, some years the flu vaccine is more protective than in other years, i.e. the vaccine is a closer match to the actual flu virus that turns out to be the major contributor to disease that year.
What about pandemic flu, you ask? It results from a slightly different process known as antigenic shift. Antigenic shift, which may be much more sudden than antigenic drift, occurs when the segments of the human flu virus re-assort and attach to segments of animal viruses—think swine flu, bird flu, and so on. (I couldn’t think of a tasteful G-rated way to include antigenic shift in my little noir anecdote—any references to bestiality wouldn’t have gotten past the censor in the 1940s. [Ed: Or in PopSci today, for that matter.])
Anyway, what everyone always wants to know is whether you can actually get the flu from the flu vaccine. The answer is “no”—the standard vaccine (with the needle) is made from killed virus; there is no way for the dead virus to give you the flu. The nasal spray vaccine, which is available for certain people without other health conditions, is made from attenuated virus, which means the virus is weak, too weak to actually give you the flu. After either vaccine, some people may feel achy and feverish for a day or two, but this is just your immune system revving up in case it needs to recognize the real flu in the future. Most people feel fine, and those who feel lousy get better in a day or two.
So if your doctor offers you a flu shot—go for it. A season’s worth of protection from disease is nothing to sneeze at.