Pfizer COVID-19 shot won't be ready for youngest kids for months: 'Might be a three-dose vaccine'

• Pfizer hopes a third dose of its COVID-19 vaccine eight weeks after the first two shots will provide the desired effectiveness in early trials.
• Other vaccine makers have lagged Pfizer-BioNTech in trials for children, which is why that vaccine remains the only one authorized for minors.

Pfizer-BioNTech's COVID-19 vaccine won't be available anytime soon for kids younger than 5.

In early tests, the lower dose given to 2- to 5-year-olds didn't produce as much immune protection as did shots given to other age groups, a Pfizer scientist said at a federal advisory committee meeting Wednesday, expanding on information provided late last year. 

The company hopes a third dose of vaccine eight weeks after the first two shots will provide the desired effectiveness, Dr. Alejandra Gurtman, vice president of vaccine clinical research and development for Pfizer said at a meeting of the Advisory Committee on Immunization Practices.

But that means waiting until late March or early April for results, she said, allowing time for children in the trial to get a third shot and then have their immune responses tested.

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"This might be a three-dose vaccine," Gurtman said, adding that Pfizer-BioNTech is testing a third dose in children ages 5 to 12, as well.

The vaccine has been shown to be safe in younger children, she said, as it was for older children and adults.

In 2020, Pfizer-BioNTech ran a 40,000-person trial to prove effectiveness in people 16 and older. But as is standard with vaccines like the flu, the Food and Drug Administration allowed Pfizer-BioNTech and other COVID-19 vaccine-makers to run much smaller trials in other age groups.

The companies just have to show that immune responses are comparable – which has been true for every group except the 2- to 5-year-olds.

Younger children were given a 3-microgram dose of the same vaccine given to adults and adolescents at 30 micrograms and to children ages 5 to 12 at 10 micrograms. Children ages 6 months to 2 years did mount an adequate immune response at that 3-microgram dose, Gurtman said.

On Wednesday, the advisory committee recommended children ages 12 through 15 become eligible for booster shots of the Pfizer-BioNTech vaccine, so now everyone ages 12 and up is recommended to receive a booster. People 12 and up who are immunocompromised are also eligible for an additional dose.

Other vaccine makers, including Moderna, have lagged Pfizer-BioNTech in trials for children, which is why that vaccine remains the only one authorized for minors. 

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The FDA is exploring options for speeding up vaccines for the youngest children, Dr. Doran Fink, deputy director of the FDA's division of vaccines and related products applications, told the committee.

"We're evaluating what options are possible for moving forward with evaluating the vaccine in this age group," he said, "in order to figure out how to best make available safe and effective vaccine as quickly as possible."

Contact Karen Weintraub at kweintraub@usatoday.com

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