Normally, an adult requires a booster once in ten years to remain up to date;
most of us go a lot longer between boosters and do just fine.
I would suspect that if your daughter was previously immunized a year or two
would not be a problem since an incident like stepping on a nail would
automatically place her (or anyone else) on the 'priority' list for an
immediate booster shot.
They are giving it out without a problem in such cases.