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Pfizer says booster in children 5-11 raises antibodies against omicron

The company says it plans to submit its data to the FDA for authorization.
Image: Child vaccine
A child receives the Pfizer-BioNTech Covid-19 vaccine at the Jewish Federation/JARC's offices in Bloomfield Hills, Mich., on May 13, 2021.Jeff Kowalsky / AFP via Getty Images file

A booster dose of the Pfizer-BioNTech COVID-19 vaccine raised antibody levels in children ages 5 to 11, the company said Thursday.

The additional shot, given six months after the two-dose primary series, led to a sixfold increase in antibodies against the original strain of the coronavirus.

The clinical trial of the booster shot included 140 children ages 5 through 11. In a smaller sub-analysis of 30 kids in the trial, Pfizer said the additional dose led to a thirtysixfold increase in antibodies against the omicron variant of the virus.

Pfizer announced the trial results in a news release. The data have not yet been made available to outside scientists for review.

Related: Will the BA.2 variant cause another COVID-19 surge? Here’s what we know

Pfizer’s COVID vaccine for kids 5-11 comes in a smaller dose than its vaccine for people ages 12 and up: 10 micrograms, compared to 30 micrograms. The booster shot is also 10 micrograms.

In February, researchers from New York State Department of Health reported that two doses of the Pfizer vaccine offered little protection against infection in children in this age group, with the vaccine’s effectiveness falling to 12% in December and January.

The Centers for Disease Control and Prevention later reported that the two doses for children still protected strongly against severe outcomes of COVID-19, including hospitalization and death.

In that report, CDC researchers said the omicron variant was the reason the shots’ protection fell so low. The omicron wave led to a record number of cases in children, compared to earlier waves.

Less than 30% of children ages 5 to 11 have received two doses of a vaccine, according to new data from the CDC.

Pfizer said it plans to submit its data to the Food and Drug Administration in the coming days for emergency use authorization. Currently, Pfizer boosters are available only to people ages 12 and up.