The recent CDC study [1] suggests that vaccine efficacy against hospitalization for people 65+ is ~80% in the US. If we have reason to believe that a third vaccine dose would increase that efficacy, and the immunological data suggests that we do, then IMO it's clearly the right thing to do. Incontrovertible data will mean many seniors being hospitalized and dying in the interim.

There's so much we can do to increase the global supply of vaccines without sacrificing American citizens. Let's focus on those things to improve vaccine equity.

[1] https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e3.htm