Nikhil Prasad Fact checked by:Thailand Medical News Team Sep 16, 2026 1 hour ago
An Israeli study examining internal pharmacovigilance records has raised questions about how quickly an emerging myocarditis and pericarditis safety signal was communicated during the early COVID-19 vaccination campaign.
Researchers Yaakov Ophir, affiliated with Ariel University in Israel and the University of Cambridge in the United Kingdom, and Yaffa Shir-Raz of the University of Haifa in Israel, analyzed an anonymized Israeli Ministry of Health dataset containing serious adverse-event reports sent to Pfizer between March 2021 and May 2022.
Israeli researchers identified a prominent myocarditis and pericarditis pattern in internal vaccine safety reports, particularly
among younger males.
Hundreds of Hospitalizations Examined
The dataset contained 531 hospitalization records and 67 unique deaths. The researchers stressed that these were pharmacovigilance reports, not proof that vaccination caused the events, and the dataset cannot calculate population-level incidence or risk.
The median reported interval between vaccination and hospitalization was five days, while the median interval between vaccination and death in the deaths worksheet was three days.
Of 530 hospitalization records with valid age information, 211, or 39.8%, involved people younger than 30. Among them, 134, or 63.5%, had no meaningful medical history identified under the study definition.
Myocarditis Signal Concentrated in Younger Patients
The standout finding involved myocarditis and pericarditis. These diagnoses appeared in 250 of 531 hospitalization records, or 47.1%. Among patients under 30, the proportion climbed to 151 of 211, or 71.6%, including 48 patients younger than 18.
Among 134 patients under 30 without meaningful medical history identified, 99, or 73.9%, had myocarditis or pericarditis. Of those 99 patients, 90, or 90.9%, were male.
Exploratory analysis found myocarditis or pericarditis in 71.6% of reports involving people under 30 versus 31.0% among older patients. Within the under-30 group, rates were 82.9% among male records and 31.9% among female records.
Questions Over Timing of Warnings
According to the study covered in this
Thailand Medical News report, Israel alerted the CDC and European Medicines Agency to about 40 myocarditis cases by late February 2021. By March 25, the spreadsheet showed 157 hospitalizations and 46 deaths reported to Pfizer, including 65 myocarditis or pericarditis cases.
The researchers argue broader communication to clinicians and the public followed roughly three to four months later and generally emphasized that myocarditis was rare and usually mild.
Important Limitations and Conclusions
The authors emphasized that the records lack a population denominator and cannot establish causality, incidence, or comparative population risk. Dataset completeness also could not be established.
The findings document a pronounced concentration of
reported myocarditis and pericarditis, particularly among younger males, while raising questions about the timing of safety communication. However, they cannot determine whether vaccination caused individual events or quantify risk across the vaccinated population.
The study findings were published in the peer reviewed EXCLI Journal.
https://www.excli.de/excli/article/view/9596
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