A health worker administers a dose of a Pfizer COVID-19 vaccine during a vaccination clinic earlier this month at the Reading Area Community College in Reading, Pa.

A health worker administers a dose of a Pfizer COVID-19 vaccine during a vaccination clinic earlier this month at the Reading Area Community College in Reading, Pa. / AP

Updated September 20, 2021 at 10:31 AM ET

The first results from the highly anticipated trial studying the effectiveness and safety of the Pfizer and BioNTech COVID-19 vaccine for children ages 5 to 11 showed promising results.

The pharmaceutical companies said early results of their trial indicate the vaccine is safe for children and establishes a strong antibody response against the virus.

Giving a two-dose regimen of 10 μg (micrograms) administered 21 days apart for children between 5 and 11 years old was well tolerated, according to Pfizer and BioNTech. Side effects were also generally comparable to those of people between the ages of 16 and 25 years old who received the vaccine.

This trial used a smaller vaccine dosage, 10 micrograms, rather than the 30 microgram dose used for people 12 and older. The dosage was selected as the preferred dose for safety and effectiveness in young children.

News of the results come as pediatric cases of COVID-19 are increasing amid a nationwide surge of infections.

"Since July, pediatric cases of COVID-19 have risen by about 240 percent in the U.S. — underscoring the public health need for vaccination. These trial results provide a strong foundation for seeking authorization of our vaccine for children 5 to 11 years old, and we plan to submit them to the FDA and other regulators with urgency," said Albert Bourla, the chairman and CEO for Pfizer.

"Over the past nine months, hundreds of millions of people ages 12 and older from around the world have received our COVID-19 vaccine. We are eager to extend the protection afforded by the vaccine to this younger population, subject to regulatory authorization, especially as we track the spread of the Delta variant and the substantial threat it poses to children," Bourla said in a statement.

Despite the strong results, it will be some time before the general public can see an official rollout of vaccines for children ages 5 to 11. Once analysis of the trial is completed, Pfizer and BioNTech will submit the results "in the near term" to the Food and Drug Administration for review and possible emergency use authorization.

And even if the FDA grants that authorization, Dr. Francis Collins, director of the National Institutes of Health, recently told NPR that parents and caregivers will likely have to wait until the end of 2021 before a COVID-19 vaccine is fully approved for young children ages 5 to 11.

Trial results for children under 5 years of age could come later this year, the pharmaceutical companies said.

"Already in March 2021, we have started the study to evaluate the immunization of younger children. Our objective was to generate and submit the data for schoolkids to regulatory authorities around the world before the winter season begins," BioNTech CEO and co-founder Ugur Sahin said.

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Tags: COVID 19  Pfizer-BioNTech  coronavirus  Vaccines  Series: The Coronavirus Crisis