Is it acceptable to write the expiration date (the “Beyond Use Date”) of an opened vaccine multidose vial on the box rather than the vial or must it be written on the vial?

It is acceptable to put the Beyond Use Date (BUD) on the packaging; this may help when reviewing inventory. But a provider should always read the label on the vial before administering a vaccine. It is possible for a vial to be placed in the wrong box. So, the vial label is the safest place to put the BUD. Vial labels are small, and it may require putting an extra sticky label on the vial.