I dealing some on the distribution side of this. NYT has a pretty good article explaining all the infrastructure that is being rolled out. (1)

Even dry ice in coolers is low tech but gets you a lot of time considering storage for the second booster dose will be centralized.

The risk is real though. Breaks in cold chain storage have inactivated vaccines have been documented to leading to outbreaks in other disease states. Still, at this point, from my boots on the ground perspective -- so far, so good.

1. https://www.nytimes.com/2020/09/18/business/coronavirus-covi...