The FDA has decided to delay a decision on authorizing Moderna Inc.’s Covid-19 vaccine for adolescents to assess, the shot may lead to heightened risk of a rare inflammatory heart condition, according to people familiar with the matter.

The FDA has been taking another look at the risk of the condition, known as myocarditis, among younger men who took Moderna’s vaccine, especially compared with those who received the vaccine from Pfizer Inc. and BioNTech SE, the people said.

Moderna Chief Medical Officer Paul Burton said the FDA’s own data on vaccinations among 18-to-25-year-olds does not show any significant difference in the rate of myocarditis among people who took the Moderna or Pfizer-BioNTech vaccines.