Pfizer Says Strong Response From 3 Covid Vaccines In Young Children

Pfizer and BioNTech said Monday that preliminary findings from a clinical trial of children under five showed that three doses of their coronavirus vaccine produced an immune response strong enough to meet criteria for regulatory clearance.

In a news release, the companies announced the results of a subset of a trial of 1,678 children aged 6 months to 4 years, saying the three-dose regimen had been 80 percent effective in preventing symptomatic infections. No supporting data was disclosed, and the companies did not say how many children were in the subset. A Pfizer spokeswoman said full trial results will be released next month.

Both Pfizer and Moderna hope to soon obtain authorization to vaccinate the nation’s youngest children. About 18 million children under the age of 5 are the only Americans not yet eligible for coronavirus vaccination, and parents’ expectations about when vaccines will be offered have been repeatedly dashed.

Pfizer and its partner BioNTech said the number of children in the trial who got sick with Covid was too small to make a definitive statement about efficacy. Only 10 children who participated in the trial became ill with Covid after those in the vaccination group received the third dose. The clinical trial protocol specified that the analysis of the efficacy of the vaccine required at least 21 cases of Covid. The companies said final data on efficacy, a secondary endpoint for the clinical trial, will be shared “once they become available.”

The Biden administration hoped to offer vaccine doses to those under 5 years of age beginning in February. The Food and Drug Administration initially pushed Pfizer to submit data on how well two doses worked for young children, but withdrew after Pfizer said two doses were not effective enough to prevent symptomatic variant infection. Highly contagious Omicron.

But Pfizer said the new results showed that three doses, with the third given at least two months after the second, stimulated the immune system to strongly protect against the virus, with no safety concerns. The researchers said the immune response of the subset of trial participants, measured one month after the third dose, compared favorably with that of people ages 16 to 25 who received two doses.

“We are pleased that our formulation for the youngest children, which we carefully selected to be one-tenth of the adult dose, has been well tolerated and produced a strong immune response,” said Dr. Albert Bourla, CEO of Pfizer, in a statement. Dr. Ugur Sahin, CEO of BioNTech, said the companies will complete their FDA application for emergency authorization of the pediatric vaccine this week.

The new findings ignite a competition between Moderna and Pfizer over which company will produce the best vaccine for the youngest Americans. Moderna proposes a two-dose regimen for children under 6 years of age, using one quarter of the strength of its adult dose. The company has said it anticipates a third dose will be needed as a booster injection, but has not yet submitted any data to the government.

The question of which vaccine works best will come before a committee of outside FDA advisers, likely in mid-June. With Pfizer and Moderna proposing different dosing regimens for younger children and presenting different clinical trial results, the committee could influence regulators on which vaccine should be authorized, or whether both deserve authorization.

In late April, Moderna applied for emergency authorization of its pediatric vaccine after interim results showed that clinical trial participants had an immune response similar to that of young adults when given a dose a quarter of the the same.

Like Pfizer, the firm said its results met the success criteria for clinical trials. Moderna has said its vaccine appeared to be 51 percent effective against symptomatic infection among children younger than 2 years old, and 37 percent effective among those 2 to 5 years old.

If Pfizer’s results are confirmed by later data, its effectiveness would be better than Moderna’s. Both companies say their vaccines produce side effects similar to those of other pediatric vaccines that have been used for decades.

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