Cardiac Events Following JYNNEOS Vaccination for Prevention of Monkeypox

PurposeThe JYNNEOS vaccine is an FDA-approved vaccine indicated for prevention of smallpox and monkeypox that is currently being distributed to high-risk individuals to combat the monkeypox public health emergency. The FDA safety data for JYNNEOS vaccine notes potential cardiac adverse events of special interest (AESI) following vaccination. 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. Our objective was to describe the incidence of cardiac AESIs in the Kaiser Permanente Northwest (KPNW) population who received a JYNNEOS vaccination for prevention of monkeypox. MethodsWe conducted a retrospective cohort study of 2,126 KPNW patients aged 12 or older who were vaccinated with at least 1 dose of JYNNEOS vaccine between July 14th 2022 and October 10th 2022. We searched KPNW databases, including the electronic health record (EHR), for diagnoses of elevated troponins, chest pain, myocarditis, pericarditis, myopericarditis, acute myocardial infarction, cardiac dysrhythmia, cardiac arrest, or ventricular fibrillation that were documented during any encounter (visit) using ICD-10-CM diagnosis codes. Two KPNW physicians reviewed all possible cases in the EHR to adjudicate cases as cardiac AESIs in alignment with the case definition used in the FDA safety data. ResultsThere were 2,126 KPNW members who received a total of 3,235 JYNNEOS vaccine doses between July 14th and October 10th. Encounter ICD10 diagnosis codes and troponin values identified 24 possible cardiac AESI cases. After physician adjudication, there were 10 confirmed cardiac AESI for an incidence of 3.1 per 1000 doses given with (exact 95% CI, 1.5 to 5.7). Of these 10 events, none could be attributed directly to the vaccination. ConclusionThe incidence of cardiac adverse events following JYNNEOS vaccination for prevention of monkeypox is unknown and this is the first study to evaluate cardiac AESI following JYNNEOS vaccination in the 2022 monkeypox public health emergency. This retrospective cohort study of JYNNEOS vaccination for prevention of monkeypox identified 10 cardiac events that all had alternative explanations; and no hospitalizations or serious adverse outcomes were attributed to vaccination. 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.