The Pfizer vaccine, along with its likely successors, is a very good thing for the U.S. and the world. Yet it's also likely to reshape America in some unsettling ways, segregating society more tightly into rational and irrational responders, especially in the short run.
The first issue will be how Americans respond over the course of the next few months. Simple logic suggests that when a good vaccine is pending, you should play it much safer. Instead of putting off that vacation indefinitely, just wait until you're vaccinated, possibly as soon as next summer. In theory that should be an easier adjustment to make, as indicated by what economists call "intertemporal substitution": waiting for a short time is easier and less costly than waiting for a long time.
Many people will behave in such a rational fashion. But many will instead take more risk. As the prospect of a post-COVID America becomes more vivid, the temptations of going out and socializing now will become more powerful. Once people start thinking about the imminent prospect of partying and fine dining, they might find it harder to resist the idea of just going ahead with it now, despite the higher risk. The giddiness occasioned by a vaccine might have some counterintuitive and negative effects.
Of course, some truly rational and forward-looking people will realize that some of their friends and contacts will behave in this less responsible manner. The more rational among us thus will take greater care to avoid those whom they do not trust, as well as those who have front-line service jobs and thus cannot avoid contact with these less responsible individuals. The rationalists will cocoon themselves more, most of all from strangers and known irrationalists.
Another possibility is that norms of social scorn will weaken, and confusion will reign for a while. Currently, if you shop without a mask or hog the middle of the jogging path in the park, you will be asked to leave or given dirty looks. These are healthy social reactions that help to keep the virus under control.
Will that remain the case once 10% or 20% of the population has been vaccinated? Furthermore, by then a higher percentage of the population already will have had COVID-19. You could imagine that, by February or March, 30% to 40% of the American population either will have had COVID (a form of vaccination in fact, albeit a dangerous one), or have received a proper vaccine. Many of them will take off their masks in public spaces.
Will you still be so inclined to give non-mask-wearers dirty looks? Their behavior might be just fine and pose no risk to others or you. And the vaccinated will themselves be less likely to give dirty looks to other non-mask-wearers, because they will not personally feel so threatened.
In other words, some highly useful norms may end up weaker during the transition phase. People who remain unvaccinated and vulnerable may temporarily face higher rather than lower risks.