The Pfizer vaccine for kids ages 5 to 11 is 10 micrograms, roughly one-third of the dose given to adolescents and adults.
In data presented to the FDA ahead of the agency’s review of its shots for children, the company described the interim results of two ongoing studies testing the safety and effectiveness of its 10-microgram shots.
The vaccine effectiveness data comes from a study of more than 2,000 kids ages 5 to 11. Two-thirds of the children were randomly assigned to receive a child-sized dose of the Pfizer-BioNTech vaccine, while the other third was sorted into the placebo group.
The study got underway as the Delta variant became dominant around the world. As of the first week of October, 16 participants in the placebo group had gotten a symptomatic, lab-confirmed COVID-19 infection, compared with just three who caught COVID in the vaccinated group.
Kids also could have swollen lymph nodes after their vaccinations, as adults sometimes do, but these reactions were temporary.
One child developed a tic, a recurring involuntary muscle twitch or vocal sound, that came one week after their second dose of the vaccine. It was judged by study investigators to be related to the vaccine. The company says it was going away by the time the study was being published.
Reassuringly, no cases of heart inflammation called myocarditis were found in the study. Myocarditis is rare and temporary, but it requires hospital care. The highest rates of myocarditis have been seen in males younger than 30. That group has a risk of about 11 cases for every 100,000 doses given, according to a recent study in the New England Journal of Medicine.