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The “Hotel Influenza” probably won’t appear in any of your Priceline searches for St. Louis, Missouri. If it does, then it better not charge you any money.

No, instead the Extended Stay Research Unit at St. Louis University’s (SLU) Center for Vaccine Development (dubbed the “Hotel Influenza” in their press release written by Nancy Solomon) will pay you around $3500 (which also will cover travel expenses) to stay in hotel-style rooms, equipped with private bathrooms, televisions, the Internet, and common areas with comfy chairs. You also get catered meals in the dining room and kitchen area, access to exercise equipment, and nice views of the St. Louis Arch.

Let’s see, what else?  Oh, at the “Hotel Influenza,” you get intentionally exposed to the influenza virus. Such a lovely place.

Anything unusual about these arrangements? Not used to having comfy chairs? Think televisions are unusual in a hotel? Oh, yes, you are wondering why you need to get exposed to the flu virus?

That’s the catch, or what you may catch, when staying at the “Hotel Influenza.” The Unit is for conducting human challenge studies. In a human challenge study, humans are deliberately exposed to something, usually unpleasant or potentially harmful. That’s why it is called a “challenge” study rather than a “wonderful feeling” study or “easy street” study and you don’t tend to hear of compliment or yummy food challenge studies.

In this case, if you volunteer, you first receive a flu vaccine or a placebo (i.e., a fake vaccine) and then later get exposed to the flu virus. For example, someone may shove the flu virus up your nose. Researchers can culture the flu virus in a lab and put it on a big Q-tip, which then goes right up your nostril. Yes, any time of year, any time of year, you can find flu here.

Then, the research staff is programmed to receive, following and testing you to see if you actually develop the flu and flu symptoms. You can’t quite check out any time you’d like. The study lasts long enough to ensure that you are no longer shedding virus (usually about ten days) and thus may infect others outside the research unit.

Why do all this? This may be the best way to measure how effective a flu vaccine may be at preventing the flu. Such a study can help determine the efficacy of a flu vaccine, which is the number of people who develop the flu after being exposed to the virus divided by the total number of people exposed to the virus.

Otherwise, determining how well a vaccine can protect you may be, uh, challenging. These days many studies trying to measure flu vaccine effectiveness are actually more correlation or association studies. These studies will compare two groups of people: those who got the flu vaccine and those who did not. Researchers then try to measure who got sick over the many month course of a flu season.

The trouble is such a study doesn’t measure who actually got exposed to the flu virus and to what degree. There’s a big difference in exposure risk for a pre-school teacher who regularly has to touch snot-covered things (and may be snot-covered himself or herself) versus a person who rarely leaves the house. Moreover, figuring out whether someone actually got the flu and developed symptoms over the course of the lengthy flu season (which can last for over 6 months) can be challenging. Many other illnesses have symptoms like the flu but are not the flu. In fact, you may catch the flu but never develop any symptoms