Countries looking out for themselves in this fashion likely behave shortsightedly. Having Covid ravage e.g. Brazil and in effect use this country as a bioreactor for mutations does put e.g. the US at grave risk.

Now Brazil has other problems than vaccine availability, but the principle of altruism being in the own interest still is valid.

This is a tragedy of the commons that is very tragic indeed. And very little seems to be done to combat the demagogy.