This study is looking at a new type of COVID-19 vaccine for children. It's called a variant-adapted BNT162b2 RNA-based vaccine, which means it's designed to work against different versions of the virus. The study is split into 5 groups, or substudies, based on the children's age and how many COVID-19 shots they've had before. Some kids will get up to four shots, while others might get just one.

To join, children must be healthy and meet certain age requirements. Some children can't join, like those with certain medical conditions or who have already had a different COVID-19 vaccine. The study checks how safe the vaccine is and how well it helps the body fight the virus.

• There are 5 separate groups based on age and previous COVID-19 shots.
• Children in the study will get 1-4 shots, depending on their group.
• Participants must be healthy and meet specific criteria to join the study.