Pfizer COVID-19 booster provides strong immune boost in kids ages 5-11, new study shows

Healthy children ages 5 to 11 mount a safe, strong immune response to the Pfizer-BioNTech COVID-19 booster, according to a new study from the companies.

Blood samples from 30 children who received a third shot showed a 36-fold increase in antibodies against the omicron variant of the coronavirus. In 140 children, a third dose increased antibodies sixfold against the original strain of the virus.

Because the vaccine is approved for adults, regulators allowed immune responses to be used as a metric of effectiveness, instead of actual infections. No new safety issues arose among the 400 children in the booster trial.

The positive results "reinforce the potential function of a third dose of the vaccine in maintaining high levels of protection against the virus in this age group," according to a Pfizer news release. 

The companies plan shortly to ask the Food and Drug Administration to authorize booster shots for children ages 5-11.

Children in that age group receive a 10-microgram dose of the Pfizer-BioNTech vaccine, one-third the dose given to adults. In the study, they were given a third dose six months after the second.

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No vaccines have been authorized for children under 5, as trials are underway. Pfizer-BioNTech found that two vaccine doses, though safe, provided too few antibodies in children ages 2 to 4 and were not likely to be protective. 

The companies are testing the third shot in that age group. The Pfizer-BioNTech vaccine is the only one authorized for use in children.

Pfizer-BioNTech's studies have included more than 10,000 children under 12 in the USA, Finland, Poland and Spain.

The Centers for Disease Control and Prevention authorized vaccines for children ages 5 to 11 in early November. There are approximately 28 million American children in that age group, and about 10 million have received at least one dose, according to the CDC.

Contact Karen Weintraub at

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