Moderna had conducted clinical trials on at least 3,732 participants aged between 12 and 17 years. No cases of COVID-19 were observed in any of the vaccinated participants and "no significant safety concerns" were identified, as per study results.
source https://www.jagranjosh.com/current-affairs/modernas-covid19-vaccine-100-percent-effective-in-adolescents-aged-between-1217-years-1622027722-1