"These topline safety, immunogenicity and efficacy data are encouraging, and we look forward to soon completing our submissions to regulators globally with the hope of making this vaccine available to younger children as quickly as possible, subject to regulatory authorization," Pfizer Chairman and CEO Albert Bourla said in a statement. The vaccines for this youngest age group are smaller than those used in older age groups. People age 12 and older receive two doses of a 30-microgram vaccine and children ages 5 to 12 receive two doses of a 10-microgram vaccine. Both age groups are eligible for booster doses. For children 6 months to 5 years, the Pfizer/BioNTech vaccine is three 3-microgram doses. The initial two doses were given three weeks apart, and the third dose was given at least two months after their second dose. Children younger than 5 are the only age group not yet eligible for vaccination against Covid-19.