Moderna Inc. /zigman2/quotes/205619834/composite MRNA -4.45% said it would delay filing a request with the U.S. Food and Drug Administration to emergency use authorization of its COVID-19 vaccine at the 50 µg dose level in children ages 6 to 11, to give the regulator time to complete its review of an earlier submission for use in adolescents 12 to 17 years of age. The company announced the news in a Sunday release, in which it said the FDA had informed it that it needed more time to complete its assessment of the request for the 100 µg dose level in 12-to-17-year-olds. The agency told Moderna late Friday that it would need more time to review the data on the risk of myocarditis after vaccination. It said the review may not be completed before January of 2022. "An increased risk of myocarditis has been described for COVID-19 vaccines, including the Moderna COVID-19 vaccine, particularly in young men and following the second dose," the company said. It noted that both the U.S. Centers for Disease Control and Prevention and the World Health Organization have said that myocarditis following vaccination with mRNA vaccines has been "rare and generally mild." About 1.5 million adolescents have received the Moderna vaccine and the rare condition has been showed to be an increased risk in that age group, said the release. Moderna shares were down 2.2% premarket but have gained 240% in the year to date, while the SPDR S&P Biotech ETF /zigman2/quotes/205950134/composite XBI -2.11% has fallen 11% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.89% has gained 22.6%.