Nothing, it's in everyone's best interest to share a vaccine with the entire world. A vaccine for this is not something to profit from.
Moderna intends to profit from a vaccine, should theirs prove successful (that is, they will not sell it at cost).[1]
The US has already made efforts to buy up a vaccine supply and withhold it from other nations.[2]
[1] https://www.ft.com/content/405c0d07-d15a-4f5b-8a77-3c2fbd5d4...
[2] https://www.politico.eu/article/germany-confirms-that-donald...