UPDATE: Novavax’s stock slides 23% after FDA details myocarditis cases for COVID-19 vaccine candidate

Shares of Novavax Inc. tumbled 22.9% in trading on Friday after the Food and Drug Administration published a report that detailed the agency’s assessment of the clinical data for the company’s COVID-19 vaccine candidate. There were at least four instances of myocarditis, a type of heart inflammation, in the clinical-trial participants. “If causally associated, the risk of myocarditis following NVX-CoV2373 could be higher than reported during post-authorization use of mRNA COVID-19 vaccines,” the FDA said. No cases of myocarditis were reported in clinical trials for either of the approved mRNA vaccines, which were developed by Moderna Inc. and BioNTech SE [sbntx] and Pfizer Inc. . The first reports about myocarditis came after the mRNA vaccines had already been authorized. The FDA report was released in advance of next Tuesday’s meeting of the Vaccines and Related Biological Products Advisory Committee. The two-shot vaccine has a 90% efficacy rate against mild to severe symptomatic COVID-19. Novavax’s stock is down 70.0% this year, while the broader S&P 500 has declined 12.3%.

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