operations and the logistics. so as soon as we have both the fda authorization and the cdc recommendations, there will be vaccine out there, so children can start rolling up their sleeves. >> reporter: 28 million children in the u.s. would be newly eligible. pfizer's early trial data showing the vaccine, one-third the adult dose, is nearly 91% effective against symptomatic illness in young children. also reporting zero cases of myocarditis, inflammation of the heart muscle, occurring most often in young men a few weeks after the second shot. >> the younger age group had less severe side effects than even the older kids. that's probably because it's a smaller dose. >> reporter: renee and miguel chavez's two children, nico and sofia, took part in the pfizer trial. >> we all got vaccinated, and it was extremely important to us tat our kids were kept safe from covid as well. >> reporter: meantime, a massive booster rollout kicking off. more than 12 million americans already getting that additional shot. >> i'm so excited to get this booster. i'm very excited.