Playing Hard to Get: the Strange Psychology of Vaccine Shortages

So far, the biggest problem with the swine flu vaccine seems to be that it is hard to find. This may not be a bad thing, at least not from a public-health perspective. If the vaccine were easy to find, fewer people would want it. It’s perverse but true. Long lines can be good for your health.

When humans are faced with a shortage of a commodity, they tend to want more. In a bar, the research shows, men and women tend to view each other as increasingly attractive the closer it gets to closing time. Same thing goes for vaccines. From a 2008 paper, “Short on Shots,” out of the Univ. of California, Berkeley:

“[P]erceptions of scarcity can induce a sharp increase in demand due to rising salience of the scarce good, worsening whatever true shortage there might be. Some of the great famines in history like those in Bengal in 1943, Ethiopia in 1973, and Bangladesh in 1974 in fact occurred without any disruption in supply (Sen, 1981). The “Great Toilet Paper Shortage’’ caused in zest by Johnny Carson in 1973 also occurred without any change in supply.”

The rest of this study is even more interesting. The researchers took advantage of the 2004 flu-vaccine shortage to see how changes in supply—and rhetoric—can influence demand.

Here’s how they did it: At one university campus, the researchers sent one group of departments an email warning of shortages in the vaccine supply and setting out a schedule for vaccinations. Then the researchers sent another email to another group with the same information plus a request (much like the one made nationally by the Centers for Disease Control and Prevention at the time) that people outside the high-risk groups hold off on getting vaccinated.

Well, a few interesting things happened. First, there was an overall increase in demand for the vaccine, now that there was a shortage. This was true all over the nation that year, by the way. Many people who had not been vaccinated before suddenly wanted the vaccine, now that it was hard to get.

But something even more suprising happened at this particular campus clinic. The request for non-high-risk people to show restraint seemed to backfire—leading to exactly the opposite result! Among the group that received that appeal for benevolence, more people came out to be vaccinated. Most perversely of all, the increase was due entirely to people in the non-priority groups. People in the high-risk groups? Well, they seemed to listen to the call for restraint and stay home…

A nice example of how very complex it can be to try to engineer human behavior during a pandemic.

So far, the best advice I have seen for how to improve the long lines came from one of the people waiting in such a line: “Letting some coffee vendors know about us here would…be a nice thing,” Dan Orbach told a Washington Post reporter, outside of a Montgomery County, MD, clinic yesterday.