A third pediatric dose of the Pfizer-BioNTech COVID-19 vaccine in children 6 months to under 5 years of age prompted a strong immune response, with a safety profile that was similar to placebo, the companies said.

Pfizer's pediatric COVID-19 vaccine has an efficacy of 80.3%, according to a preliminary analysis, and meets "all immunobridging criteria required for Emergency Use Authorization," the company said Monday. The results are based on clinical trials in which kids from six months to age 5 got three doses of the company's vaccine.

Pfizer and its partner, BioNTech, plan to submit the new data to the Food and Drug Administration this week, bringing families with young children one step closer to a long-awaited vaccine.

The size of Pfizer's pediatric dose is one-tenth of its adult dose. The company had originally tested a two-dose regimen, but mixed results prompted Pfizer to test a three-dose regimen.

The third dose was "well tolerated among 1,678 children under 5 years of age with a safety profile similar to placebo," Pfzier said as it announced the news.

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