Two studies released by the Centers for Disease Control and Prevention underscored the importance of vaccinations against the coronaviruses.
There were very few serious problems among children who had received the Pfizer-BioNTech vaccine. The other found that almost all of the children who became seriously ill had not been fully protected.
The Pfizer vaccine has been given to more than eight million children in the United States. Concerns about the unknowns of a new vaccine caused some parents to hesitate in allowing their children to be inoculated, including those who preferred to wait for the broader roll out to bring any rare problems to the surface.
The C.D.C. said that it had received very few reports of serious problems. The agency looked at reports received from doctors and members of the public, as well as survey responses from the parents or guardians of 43,000 children in that age group.
Many of the children who were surveyed reported pain at the site of the shot after the second dose. The survey found that 13 percent of people had a high temperature after the second shot.
There were no reports of myocarditis, an inflammation of the heart muscle that has been linked in rare cases to coronaviruses vaccines. The C.D.C. said there were 11 verified reports. The C.D.C. said that seven children had recovered and four were still recovering.
The C.D.C. said that reporting rates for vaccine-related myocarditis were highest among boys and men.
A number of parents and doctors reported instances of their children getting the wrong vaccine dose. The C.D.C. said that the problems were not unexpected, and that the children had no problems after.
The C.D.C. reported two deaths of girls who had chronic medical conditions and were in poor health before their shots. There was no evidence to suggest a correlation between death and vaccination.
The C.D.C. provided more evidence about the importance of vaccinations for eligible children. The study found that a small percentage of the children who were eligible for the shots had been fully protected.
Two-thirds of all the hospitalized children were obese, and one-third of children 5 and older were sick with more than one viral infection, according to the study.
Almost one-third of the children were so sick that they had to be treated in intensive care units. 1.5 percent of the children died, according to the study. The hospitals were in Arkansas, Florida, Illinois, Louisiana, Texas and Washington, D.C.
The authors of the study wrote that the study shows that unvaccinated children hospitalized for Covid-19 could experience severe disease and reinforces the importance of vaccination of all eligible children.
