The US Food and Drug Administration (FDA) approved use of the Pfizer booster for children as young as 12 years old on Monday.
The extra shot was recommended for children 12-15 years old if enough time has passed since their second dose.
Final approval for this shot for younger teens is expected to come later this week from the Centers for Disease Control and Prevention (CDC).
The CDC also reduced the time needed to wait for a booster shot from six to five months as concerns grow over the spread of the Omicron variant.
