The Food and Drug Administration (FDA) is considering revoking the authorization of Pfizer’s COVID-19 vaccine for healthy children younger than 5 years old, a move that would add another barrier for parents who want to vaccinate healthy children ahead of the respiratory virus season.

Pulling the Pfizer EUA would remove the only COVID-19 vaccine approved for all children from the US market. The Moderna vaccine is approved only for children with one or more health conditions, and the Novavax vaccine is cleared only for use in children ages 12 years and older.

Under Robert F. Kennedy Jr., federal officials may withdraw an endorsement for the vaccine in younger children.