As far as I know it's not actually true. There was some speculation that the US might ban vaccine exports, and apparently this was why the UK wanted at least on

As far as I know it's not actually true. There was some speculation that the US might ban vaccine exports, and apparently this was why the UK wanted at least one locally-produced vaccine, but I'm pretty sure only the EU actually went ahead and did it. In fact, there were some suggestions that the UK might actually have to switch its source for the Pfizer vaccine to the US as a result.