I'm not sure why this is downvoted. The quickest (perhaps only, if the timeline is short) way to comply with any US vaccination mandate is the single-shot J&J vaccine, which is basically totally ineffective at preventing Covid after a few months according to a recent VA study. But due to some weird quirks of the US vaccine approval process it's treated as equivalent to two shots of one of the mRNA vaccines and meets the vaccine mandates when being one short into an mRNA course would not, even in reality it's more like being partially vaccinated with one of those than fully vaccinated.