What you should know about coronavirus vaccines for younger adolescents

First, researchers must establish a safe and effective dose, which may be lower than the dose in adults or teens. They will do this by testing different doses, first in older children, for example 5- to 11-year-olds, before moving down to 2- to 4-year-olds and then children as young as 6 months. Then, they will test whether the vaccines are safe or effective, by measuring whether they trigger equivalent immune responses in children’s blood. Pfizer expects to have data on children as young as 2 years old by September or October, with data from younger children expected by the end of the year.