via CDC:
‘Because some traveler vaccine records might not specify whether recent Moderna or Pfizer doses received were bivalent, CDC will consider anybody with record of a single dose of Moderna or Pfizer vaccine issued on or after August 16, 2022, to meet the requirements of the Amended Order to board a plane to the United States. This date was chosen because it represents the earliest that travelers could have received a bivalent vaccine.’
h/t A Deplorable Neanderthal