Pfizer says COVID-19 vaccine safe, spurs immune response in kids ages 5 to 11

Woodruff Health Sciences Center | Sept. 21, 2021

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Jill Wu
jill.s.wu@emory.edu

Dr. Evan Anderson summarizes the information Pfizer has released on the initial pediatric trial results.

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Initial results from the Pfizer-BioNTech pediatric vaccine trial indicate that the COVID-19 vaccine is safe and triggers an immune response in children ages 5 to 11, the companies announced Sept. 20. The news arrives as the pandemic’s toll on children continues to rise; over 13% of all COVID-19 cases in the U.S. and almost 30% of all newly diagnosed cases in the U.S. are in children. The American Academy of Pediatrics has also recorded over 460 pediatric deaths due to COVID-19.

“This is a real problem for children,” says Evan Anderson, MD, professor of pediatrics and medicine at Emory University School of Medicine and principal investigator for the Pfizer pediatric vaccine trial at Emory, and physician at Children’s Healthcare of Atlanta. “As COVID-19 surges in part due to Delta, as schools begin to reopen and as parents are getting back to work and children are getting back to daycare, there is increasing parental concern about the ongoing risk for their children in the midst of daily life.”

The U.S. Food and Drug Administration has given full approval to the Pfizer vaccine for individuals ages 16 and older. Children ages 12 through 15 are able to receive the vaccine through an Emergency Use Authorization (EUA). But many parents are eager to schedule vaccination appointments for younger children. We spoke to Anderson for more clarity on what this announcement means for children.

Q: Is the vaccine for children ages 5 through 11 the same as the vaccine for adults?

A: “This is the same [Pfizer] vaccine that is used and available for children 12 and above and for adults, but it is only one-third of the dose that is used in those populations,” Anderson says. While adults and children over age 12 receive two 30-microgram doses of Pfizer vaccine, children ages 5 through 11 in the pediatric trial received two 10-microgram doses.

Pfizer-BioNTech report seeing immune responses from two 10-microgram doses in children ages 5 through 11 similar to the immune responses seen from two 30-microgram doses in individuals ages 16 through 25.

Q: Do children experience side effects from the vaccine?

A: The initial announcement indicates that children ages 5 through 11 experience similar side effects as individuals ages 16 through 25. “They did note that they had not observed any cases of myocarditis,” or inflammation of the heart muscle, Anderson says. Full safety data will be available as Pfizer sends its data to FDA for review.

Q: What is the vaccine efficacy in children?

A: Pfizer and BioNTech did not report efficacy data in their announcement. “We don’t know whether there were cases of COVID-19 among children in the study, and how those compare in those that received placebo versus those that received vaccine,” Anderson says. “I think it is possible that we may see efficacy data coming out of the Pfizer study in the future, but it does depend upon the amount of transmission that’s happening in the communities in which children are enrolled.”

Q: How does the size of this pediatric trial compare to other COVID-19 vaccine trials?

A: This trial enrolled 2,268 participants ages 5 through 11, much like the adolescent trial which provided safety data from 2,260 participants ages 12 through 15 to the FDA for review. “The studies are moving forward towards FDA licensure based off immuno-bridging, which is a method for licensure in which the immune responses in children 5 to 11 years of age are then compared to the responses observed in adults 16 to 25,” Anderson says.

Q: What is the timeline for vaccine approval in younger children?

“Right now, we don’t know,” Anderson says. Pfizer will first submit the data for children ages 5 through 11 to the FDA for review. The FDA then sets a timeline for a meeting of advisors to determine whether to issue approval. This decision requires further review by the U.S. Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices. Those experts provide additional input on how to implement vaccination.

The FDA issued an EUA for the Pfizer vaccine for adults about four weeks after receiving the data for review. For adolescents, the FDA issued an EUA around five weeks after receiving the data. Anderson says an EUA for ages 5 through 11 could follow a similar timeline, but that depends on the completeness of the data and whether the FDA has any additional questions or would like to see additional safety data.

Pfizer and BioNTech have also stated that they expect to have initial data from vaccine trials for children under 5 by the end of 2021.

Q: Will vaccinations for younger children impact community transmission?

A: “We do know that although children don’t transmit as frequently, they still absolutely can transmit COVID-19,” Anderson says. “Among the most important methods of COVID-19 transmission is in the household and from household visitors. Once it is brought into the household, it can spread from person to person. Having a vaccine available for our children will have the potential to significantly impact transmission to parents, grandparents and other adults that they come into contact with.”

Q: Will schools mandate vaccines if they are approved for younger children?

A: “I think additional data will be needed,” Anderson says. “At this point in time, it’s premature to speculate whether or not there could be school-based mandates for COVID-19 vaccination among younger children. I don’t see that happening any time in the near future.”

Q: Do vaccinated children still need to wear masks?

A: “With a tremendous amount of COVID-19 circulating, I would continue to encourage parents to follow CDC guidance and to ensure that children are wearing masks and following local school guidance,” says Anderson. He notes that the vaccine is not fully effective until two weeks after the second dose and that community transmission will need to decrease significantly before the CDC potentially relaxes masking guidelines. In the meanwhile, children should continue healthy habits such as wearing masks indoors in public, carefully washing hands, and safely distancing to prevent COVID-19 infection.