Pfizer's COVID Vaccine Produced Inadequate Immune Response In Kids Ages 2-5

Pfizer’s COVID Vaccine Trial For Kids Ages 2-5 Produces Disappointing Results

Doctor vaccinating girl in office
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The trial results are a disappointing setback that will likely delay an approved vaccine for younger kids

Pfizer-BioNTech announced on Friday that the low-dose COVID-19 vaccine they are testing on kids under 5 is not creating a significant immune response in children between the ages of 2 and 5. In other words: The trial didn’t work and they will have to go back to the drawing board.

This is not good news for the parents of young kids who have been waiting patiently for a vaccine for their toddlers.

In the ongoing clinical trial, researchers are giving kids from 6 months to 5 years a dose that is one-tenth the size of the adult dose. While it produced a satisfactory immune response in kids up to 2, the older children in the trial did not build an immune response.

Instead of trying to give the children in this age group a higher dose, the trial will try to give them a series of three shots instead of two — a change that has been approved by the Food and Drug Administration (FDA). Pfizer plans to ask for FDA authorization for a three-dose schedule for all kids sometime in the first half of 2022, mirroring the two shots and a booster approach that we’ve landed on for adults.

“The goal here is to understand the potential of protection of the third dose,” Jerica Pitts, a Pfizer spokeswoman, tells The New York Times. “We are studying 3 micrograms at this time.”

Just because the older kids in the trial did not show a significant enough response to the first two shots does not mean that all of their work is scrapped or that they have to go back to the drawing board — at least just yet. It just means that the trial will be extended for two more months so that the participants can receive the extra shot. If the immune response is still not strong enough, they may have to start a new trial that increases the dose or changes the schedule of shots for that age group.

Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia, told NBC News that even if the two shot schedule of the low dose doesn’t prevent COVID-19, it could still lessen the severity.

“To me, the goal of this vaccine is the prevention of serious illness,” he says.

In a different trial in the future, Pfizer will test a three-dose series in kids ages 5-12. The dose size for that trial will be the same as the first two: 10 micrograms, or one-third of the adult dose. Everyone over 12 receives the full adult dose of 30 micrograms.

A bit of good news? Pfizer also announced in their release that “no safety concerns were identified” in any part of the trial, which is ongoing.