These vaccines are not like the well established vaccines (such as those for polio, mumps and measles) because even though Pfizer has received "final" FDA approval, the technology behind these COVID vaccines is fairly new and therefore the long term effects cannot yet be known.  Given that children as a general matter don't seem to be as seriously impacted by COVID I think it is the right of parents - not the government - to determine the risk/reward balance for their children when vaccine becomes approved for children