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September 20, 2021

What Pfizer's clinical trial revealed about its Covid-19 vaccine in young children

Daily Briefing

    Pfizer and BioNTech on Monday announced they will file for authorization of their Covid-19 vaccine for use in children ages five to 11, citing clinical data showing the vaccine is safe and effective in children and generates a strong antibody response.

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      Details on the trial data

      For the clinical trial, researchers compared antibody responses among 2,268 children ages five to 11 with those of a group of volunteers ages 16 to 25. The children's antibody responses were also compared to those of a placebo group of similar age.

      The researchers gave the children 10 microgram doses of the vaccine, smaller than the 30 microgram doses adults receive. They found the antibody response among children was comparable to the response among those ages 16 to 25.

      William Gruber, SVP of vaccine clinical research and development at Pfizer, said the reported side effects among children, including fevers and chills, were similar to those reported among individuals ages 16 to 25.

      Pfizer's report on the trial did not directly evaluate whether the vaccine reduced children's chances of developing Covid-19. According to Gruber, there weren't enough Covid-19 cases to draw conclusions on that point.


      In a statement, Albert Bourla, chair and CEO of Pfizer, said the trial results "provide a strong foundation for seeking authorization of our vaccine for children five to 11 years old, and we plan to submit them to the FDA and other regulators with urgency."

      "There's going to be a huge number of parents who are going to heave a big sigh of relief when they hear this," Kristin Oliver, a pediatrician and vaccine expert at Mount Sinai Hospital, said. "We've been waiting for these kids to be protected."

      Kathleen Neuzil, director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine, said the data isn't "a lot to go on, but what we do have to go on looks great. A lower dose of this vaccine in children appears to be as good as the higher dose in older children and adults."

      Neuzil added that it seems children ages five to 11 are among the least likely to have severe Covid-19. "So not that it's not important and not that it's not a disease worth preventing, but if your severe outcomes are lower, then you're going to have a higher bar for the vaccine performance. You're going to want to be very careful about safety issues," she said.

      What this means for Covid-19 vaccines for children

      Gruber said Pfizer hopes to submit its data to FDA by the end of the month. Meanwhile, Pfizer and BioNTech said data on vaccines in children ages two to five, as well as for those ages six months to two years, are expected as soon as the fourth quarter of this year.

      Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he believes regulators will have enough data to make a decision on vaccines for children ages five to 11 by mid-to-late fall.

      "What we're going to almost certainly see is that sometime in the next few weeks as we get into October, we'll be able to see the vaccines for children get enough data to be presented for safety and immunogenicity," Fauci said.

      Scott Gottlieb, former FDA Commissioner and a board member at Pfizer, said it will likely be weeks before FDA authorizes Covid-19 vaccines for children ages five to 11.

      "In a best-case scenario, given that timeline they've just laid out, you could potentially have a vaccine available to children aged five to 11 by Halloween," Gottlieb said. "If everything goes well, the Pfizer data package is in order, and FDA ultimately makes a positive determination, I have confidence in Pfizer in terms of the data that they've collected. But this is really up to [FDA] to make an objective determination." (Herper, STAT News, 9/20; Oshin, The Hill, 9/19; Diaz, NPR, 9/20; Mandavilli, New York Times, 9/20; Quinn, CBS News, 9/13)

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