The US Food and Drug Administration (FDA) said on Wednesday it will add a warning about rare cases of heart inflammation in adolescents and young adults to fact sheets for the Pfizer-BioNTech and Moderna Covid-19 vaccines.

US Centers for Disease Control and Prevention (CDC) advisory groups, meeting to discuss reported cases of the heart condition after vaccination, found the risk in adolescents and young adults is likely linked to the vaccines, but that the benefits of the shots appeared to clearly outweigh the risk.

Moderna shares were down nearly four percent, while Pfizer was off 1.3 percent in late afternoon trading...