Vaccine Trial for Children Under Age 12 Has Begun, Pfizer Says

Pfizer Inc. said that dosing has begun in a pediatric study of its Covid-19 vaccine, a trial that will ultimately involve more than 4,500 children under age 12.

The two-part trial will first study three dose levels in 144 children from age 6 months to 11 years, the company said in a statement Thursday. Once an appropriate dose is established for each of three age groups, 4,500 more kids in the U.S. and Europe will be enrolled in the second part of the trial, which will look at safety tolerability and immunogenicity of the vaccine, the company said.

Two-thirds of the children in the second phase will get the vaccine, and the rest will get a placebo. After six months, all participants will be told which dose they received, a process called unblinding, and those who got a placebo will be offered the active shots.

Pfizer’s messenger RNA vaccine, developed in conjunction with partner BioNTech SE, was shown to be 95% effective in preventing symptomatic Covid-19 in a big trial. The two-dose vaccine is currently authorized for emergency use in the U.S. for people 16 and older.

Pfizer also has a vaccine trial underway in kids age 12 to 15 that is fully enrolled with 2,259 participants. Initial results from that test are expected in the coming weeks, a company spokesperson said.

Moderna Inc.’s rival messenger RNA vaccine is also being tested in young kids. On March 16, the company said it had begun a study on 6,750 kids in the U.S. and Canada ages 6 months to under 12 years. Moderna’s vaccine currently has an emergency authorization for adults 18 and older, and the company also is studying it in adolescents.

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