On May 17, 2022, the U.S. Food and Drug Administration (FDA) announced emergency use authorization (EUA) for Pfizer-BioNTech COVID-19 Vaccine as a single booster for children ages 5 to 11 who received their primary Pfizer-BioNTech COVID-19 Vaccine series at least 5 months prior. After evaluating the efficacy and safety data, the FDA concluded that the benefits of a single booster dose in children ages 5 to 11 outweigh the risks. The ongoing randomized placebo-controlled trial showed that the antibody response (a measure of how effective the vaccine is) was increased for the 67 participants who received a booster dose 7 to 9 months after completing a primary series of Pfizer-BioNTech COVID-19 Vaccine. The safety of Pfizer-BioNTech COVID-19 Vaccine as a single booster was evaluated in about 400 children, finding common side effects such as pain, redness and swelling at the injection site, fatigue, headache, muscle pain and fever, which is consistent with side effects reported from other age groups after administration of the vaccine.