While this went into effect on December 15th for those aged 65 and up, it goes into effect today for the rest of us.
If you don’t have a booster shot, you won’t be able to get a pass sanitaire. Likewise, if you obtained a pass sanitaire last summer and your booster isn’t recorded there, your pass sanitaire won’t be good any longer either; you’ll have to go to a pharmacy when you arrive and get your booster shot recorded into your pass to get it to become “live” again.
A reminder: the pass sanitaire isn’t necessary to enter France (so far you can do that with only “full vaccination” i.e. two shots of Pfizer/Moderna), but it’s necessary to enter museums, restaurants, bars, cafes, etc.