Just hours after the FDA announced full approval for the Pfizer/BioNTech Covid-19 vaccine on Monday, the AAP issued a warning: Physicians should not vaccinate any children under the age of 12 “off-label.” But by that time, parents had already started calling their pediatricians. Full FDA approval of a drug or vaccine opens the door for off-label use, when doctors can use their discretion to provide a treatment in a way other than what it’s specifically approved for — in this case, people age 16 or older.