Pfizer-BioNTech submitted data to the Food and Drug Administration to clear its Covid-19 vaccine for use in children ages 5 to 11, officials announced Tuesday.

The FDA is expected to take at least several weeks to analyze data collected in a trial that included more than 2,000 children before it would grant emergency use authorization.

A formal submission to request emergency use authorization of the companies’ vaccine is expected to follow in the coming weeks, officials said in a release.

“The FDA takes very seriously the importance of getting vaccines, shown to be safe and effective in children,” Dr. Anthony Fauci, the nation’s leading infectious disease expert, told MSNBC’s “Morning Joe” show. “I would imagine in the next few weeks they will examine that data and hopefully give the O.K. so we can start vaccinating children hopefully by the end of October.”

While the Pfizer vaccine has been available for Americans 12 and older since May, millions of elementary school-age children are still vulnerable.

Millions of those children returned to classrooms for in-person instruction in recent weeks, with some districts requiring masks and others not, in one of the nation’s most hotly debated topics.

Pfizer said its two-dose Covid vaccine has shown to be safe, while prompting a “well tolerated” and “robust” antibody response among the younger, targeted group.

The children in Pfizer’s trial were given two smaller doses of the vaccine than those given to those 12 and older, the company said. The smaller doses produced antibody responses that were comparable to those seen in a study of people 16 to 25 who received full doses. The vaccine also caused similar side effects to those seen in adults, which have included arm soreness and fatigue.

Pfizer says its Covid vaccine is safe for children ages 5 to 11

The Pfizer-BioNTech vaccine is the only Covid vaccine available to Americans under 18. In June, Moderna submitted data to the FDA to use its Covid vaccine in adolescents ages 12 to 17. Johnson & Johnson is conducting clinical trials of its one-dose vaccine in younger recipients.

Children face a much lower risk of severe disease, but as schools continue in-person classes, the need for vaccinating younger kids is important for controlling the Covid pandemic in the U.S. More than a quarter of the reported weekly Covid cases in the U.S. are in children under the age of 18, according to the American Academy of Pediatrics.

There have been more than 43 million cases of Covid confirmed in the U.S. since early 2020, which has led to at least 692,784 deaths, according to a running tally by NBC News on Tuesday.

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