Moderna Inc. held a brief conference call to defend the safety of its Covid-19 shot from a barrage of questions about associated heart risks in young people.

Chief Medical Officer Paul Burton acknowledged on the call that the company’s vaccine does appear linked to increased chances of an inflammatory heart condition known as myocarditis in young men. Moderna maintains that the shot’s benefits continue to outweigh the extremely rare risk of myocarditis, he said Thursday.

Moderna’s market value has recently taken a blow on the heart-risk concerns, along with a forecast cut and a legal battle with the government over patent rights. Shares of the Cambridge, Massachusetts-based biotech plummeted 34% this month through Wednesday’s close. They fell as much as 3.2% as of 12:16 p.m. in New York.