Based on this NYT article [1], some logistics companies planning to store and transport the vaccine are using freezers from Stirling Ultracold. It may just be a curiosity, but their freezers (as the name would suggest) use bona fide Stirling engines rather than the typical two-stage compressors used in most ULT freezers.

As someone in life science research who uses plenty of -80 freezers, I've always been curious about Stirling Ultracold. Maybe they're on to something after all.

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