Pfizer said it plans to submit to the US Food and Drug Administration for emergency use authorization soon. FDA officials have said that once data is submitted, the agency could authorize a vaccine for younger children in a matter of weeks. The trial included 2,268 participants ages 5 to 11 and used a two-dose regimen of the vaccine administered 21 days apart. This trial used a 10-microgram dose -- smaller than the 30-microgram dose that has been used for those 12 and older. "The 10 microgram dose was carefully selected as the preferred dose for safety, tolerability and immunogenicity in children 5 to 11 years of age," Pfizer said in a news release.