Scientists at the F.D.A. must then review the data, weighing the benefits of the vaccine against the risk of side effects. In rare cases, the vaccine has led to myocarditis, an inflammation of the heart, in young people.

But a large Israeli study, based on electronic health records of two million people aged 16 and older, found that Covid is far more likely to cause these heart problems.

In order to detect side effects in younger children, the F.D.A. in July asked Pfizer-BioNtech and Moderna to expand their trials to include 3,000 children. But based on the company’s conversations with the F.D.A., Dr. Gruber said he believed the agency would greenlight the vaccine with the data available so far.

The F.D.A. took about a month to review the data for adults and for adolescents. Given the escalating number of infections, the agency is under pressure to move at least as quickly to authorize the vaccine for younger children.

Parents and some public health experts have clamored for the F.D.A. to expedite its review process. Dr. Peter Marks, the F.D.A.’s top vaccine regulator, has said that without “surprises,” authorization appeared to be on track for the fall, echoing what other top federal health officials, including Dr. Anthony S. Fauci, have predicted.

“The agency will carefully, thoroughly and independently examine the data to evaluate benefits and risks and be prepared to complete its review as quickly as possible, likely in a matter of weeks rather than months,” the F.D.A. said in a statement earlier this month.

For many parents, the decision to vaccinate their children may come down to safety. Four in 10 parents of children under 12 said they would “wait a while to see how it is working” before getting their child vaccinated, according to a poll conducted by the Kaiser Family Foundation this summer.

This content was originally published here.