A non-peer-reviewed retrospective cohort study of 2,126 Jynneos monkeypox vaccine recipients identified 10 cardiac events that all had alternative explanations, and no hospitalizations or serious adverse outcomes were attributed to vaccination.
The study, published on the preprint site medRxiv, aimed to document any cardiac events after Jynneos vaccination, as the Advisory Committee on Immunization Practices (ACIP) stated that people with underlying heart disease or three or more major cardiac risk factors should be counseled about the theoretical risk for myopericarditis following vaccination with Jynneos.
The authors used vaccine recipients in the Kaiser Permanente Northwest system who were vaccinated with at least one dose of Jynneos between Jul 14 and Oct 10, 2022. The authors found there were 10 confirmed cardiac events for an incidence of 3.1 per 1000 doses given with (exact 95% confidence interval [CI] 1.5 to 5.7).
"Of these 10 events, none could be attributed directly to the vaccination," concluded the authors, who worked with a team of physicians to review events and outcomes.
"This initial study provides timely information for the clinician counseling their patient with underlying cardiac risk factors on the low observed risk of cardiac events with Jynneos vaccination during the 2022 monkeypox public health emergency."