Cardiac events following JYNNEOS vaccination for prevention of Mpox

The incidence of cardiac adverse events following JYNNEOS vaccination for prevention of mpox is unknown, however the Advisory Committee on Immunization Practices states that people with underlying cardiac risk factors should be counseled about the theoretical risk for myopericarditis following vaccination. We conducted a retrospective cohort study of 2,126 patients who were vaccinated with at least 1 dose of JYNNEOS vaccine and searched the Kaiser Permanente Northwest databases, including the electronic health record, to evaluate for cardiac adverse events of special interest (AESI). After physician adjudication, there were 10 confirmed cardiac AESI for an incidence of 3.1 per 1000 doses (exact 95% CI, 1.5 to 5.7), however none of these events could be directly attributed to vaccination. This retrospective cohort study of JYNNEOS vaccination for prevention of mpox identified 10 cardiac events that all had alternative explanations; and no hospitalizations or serious adverse outcomes were attributed to vaccination.