Real-time pharmacovigilance and cardiac risk communication during the COVID-19 vaccination campaign in Israel

During the early phase of the COVID-19 vaccination campaign, the Israeli Ministry of Health (IMOH) informed international health authorities that it had identified “a large number of myocarditis and pericarditis cases in young individuals soon after Pfizer COVID-19 vaccine.” This study discloses and analyzes an internal pharmacovigilance dataset obtained from within the IMOH to examine the case-level record associated with this early safety signal and trace how the signal was subsequently communicated to physicians and the public. The anonymized dataset, provided as Supplementary Data File 1, includes 531 hospitalization records and 67 unique deaths reported to Pfizer between March 2021 and May 2022. Reported events spanned cardiac, neurological, inflammatory, and other serious clinical categories and involved a substantial proportion of younger individuals, with 211 of 530 hospitalization records with valid age data (39.8 %) involving patients under 30 years of age. Myocarditis was recorded in two of the nine unique deaths among individuals under 50 years of age (22.2 %), while myocarditis or pericarditis was identified in 250 of 531 hospitalization records (47.1 %), rising to 151 of 211 records involving patients under 30 (71.6 %). Among younger hospitalized patients, 134 of 211 (63.5 %) had no meaningful medical history identified under the study definition; within this subgroup, 99 of 134 (73.9 %) had myocarditis or pericarditis, of whom 90 (90.9 %) were male. The safety signal was communicated to clinicians and the public only after approximately three to four months, primarily in ways that emphasized its rarity, generally mild clinical course, and lower concern relative to COVID-19 outcomes. The accuracy and completeness of this characterization, together with the implications of the case-level patterns and communication timeline documented in this study, are discussed in the broader contexts of pharmacovigilance, risk communication, and informed consent during large-scale public health interventions.