CDC recommends that people should receive the age-appropriate vaccine dosage based on their age on the day of vaccination. If a person moves from a younger age group to an older age group during the primary series or between the primary series and receipt of the booster dose, they should receive the vaccine dosage for the older age group for all subsequent doses. However, Food and Drug Administration (FDA) authorization allows for different dosing for certain age transitions. For more information see: Moderna COVID-19 Vaccine for Children who Transition from a Younger to Older Age Group Pfizer-BioNTech for Children who Transition from a Younger to Older Age Group Interim COVID-19 Immunization Schedule for 6 Months of Age and Older