On February 28, 2021, Israel’s Ministry of Health alerted health authorities on both sides of the Atlantic to an emerging cardiac safety signal following the Pfizer Covid-19 vaccine.
The warning came just over two months after Israel had launched one of the fastest vaccination campaigns in the world, placing the country at the forefront of the global rollout.
That day, the Ministry informed the European Medicines Agency that it was investigating a “safety signal of myocarditis/peri-myocarditis in the younger population (16–30 years old)” and had already received reports of around 40 cases. A CDC internal tasking memo from the same day recorded that Israel was seeing “a large number of reports of myocarditis, particularly in young people,” and was seeking contacts at the CDC and FDA to discuss the issue. The message was marked “Importance: High.”
Three days later, Dr. Roee Singer, Deputy Director of Epidemiology at Israel’s Ministry of Health, wrote directly to the CDC: “We are seeing a large number of myocarditis and pericarditis cases in young individuals soon after Pfizer COVID-19 vaccine. We would like to discuss the issue with a relevant expert at CDC.”
It was, in every sense, a “Houston, we have a problem” moment.
The alarm had been sounded. But what, exactly, had Israeli health officials seen that prompted it? And when, and how, was that warning communicated to physicians and the public?
Our newly published study in EXCLI Journal discloses and analyzes an internal Israeli Ministry of Health pharmacovigilance dataset that had never been made public. The dataset was provided to us by a whistleblower whose identity we are protecting. The file itself was titled, in Hebrew, “Reports of Hospitalizations and Deaths to Pfizer,” and contains detailed case-level reports documented by the Ministry of Health during the vaccination campaign.
The record was not reconstructed years later, after vaccine-associated myocarditis had become an established safety concern. It was being built in real time as the signal emerged.
The dataset provided to us comprised eight cumulative versions, all sharing an original creation date of March 25, 2021. The record was updated repeatedly for more than a year as new cases were added and existing reports were revised with additional clinical information. The final version extends through May 9, 2022.
Already on March 25, just over three weeks after Israel first sounded the international alarm, the record contained 157 hospitalization reports and 46 death reports. Sixty-five of the hospitalization reports involved myocarditis or pericarditis.
By the final version of the dataset, myocarditis or pericarditis appeared in 250 of 531 hospitalization reports, nearly half. Among patients under 30, it appeared in 151 of 211 reports, more than 70%.
The dataset has no population denominator, so it cannot tell us how frequently these events occurred among vaccinated people, and the reports themselves cannot establish causality. However, these were not simply reports sitting in a passive reporting system.
They documented serious events involving hospitalizations and deaths, with detailed clinical information compiled into an internal Ministry of Health record, updated over time, and reported to Pfizer for assessment. Their inclusion in this record and transmission to Pfizer indicate that the cases were considered sufficiently temporally or clinically relevant to vaccination to warrant pharmacovigilance documentation and assessment, even though causality had not been established. The Ministry itself had already identified and reported a cardiac safety signal, and the reports continued to accumulate after that warning was issued.
We analyzed the reported events, reconstructed the communication timeline, and examined when and how the signal was communicated to health professionals and the public. To enable independent examination and reproduction of our analyses, we published an anonymized version of the case-level dataset as a supplementary file, with potentially identifying information removed. The detailed reports had been compiled for Pfizer, a private pharmaceutical company and the manufacturer of the vaccine to which the reports related. Yet the underlying record had never been made public. A record documenting serious adverse events during a mass vaccination campaign should also be open to public scrutiny.
Inside the Record
The eight cumulative versions allow us to follow the record from the early months of the vaccination campaign through May 2022. As the file continued to grow, the cardiac signal did not recede. By the final version, myocarditis or pericarditis appeared in 250 of 531 hospitalization reports, nearly half. Among patients under 30, they appeared in 151 of 211 reports, more than 70%.
The concentration was even more pronounced among young males. Among males under 20, 85% of the hospitalizations involved myocarditis or pericarditis. Among males aged 20-29, the figure was 82%.
The pattern was not confined to males. Among females under 20, 11 of 16 hospitalization reports involved myocarditis or pericarditis, as did 6 of 35 among women aged 20-29.
The younger reports included a nine-year-old girl who was hospitalized after her second dose.
Among the 151 patients under 30 with myocarditis or pericarditis, 99, nearly two-thirds, had no meaningful medical history identified in the record.
The dataset also contained 67 unique deaths. Nine involved people under the age of 50. Myocarditis was recorded in two of those nine cases. One was a 22-year-old woman who developed fulminant myocarditis and cardiogenic shock after her second dose and died.
What Happened to the Warning?
The Israeli warning came on February 28. In the United States, clinicians would not receive CDC guidance on recognizing and reporting post-vaccination myocarditis until May 28.
On March 10, CDC and FDA officials circulated an internal response titled “Myocarditis Response.docx.” It noted: “The Ministry of Health stated they received reports of around 40 cases of this adverse event. They did not provide additional details about these cases.” The same response pointed to just 27 myocarditis cases reported to VAERS as of February 23. For context, Israel had a population of fewer than 10 million, compared with more than 330 million in the United States. Israel was further ahead in its vaccination campaign, but the contrast was nonetheless striking: around 40 reports in Israel, compared with 27 in VAERS in the entire United States.
On March 15, the CDC asked an Israeli Ministry of Health official to present data from Israel’s vaccine safety monitoring system to its Vaccine Safety Technical Work Group (VaST). Israel agreed. On March 24, the CDC specifically asked that the presentation address Israel’s post-authorization safety monitoring and any information on deaths reported after vaccination.
On April 5, Israeli health officials presented updated vaccine-safety data through March 31 at a VaST meeting attended by CDC and FDA officials. The presentation reported 62 cases of myocarditis or perimyocarditis, 56 of them following the second dose, as well as 15 cases of pericarditis. It also included 172 reported hospitalizations and 48 deaths reported in proximity to vaccination. Among the 56 myocarditis or perimyocarditis cases reported after the second dose, 50 were in males, with the age distribution showing a marked concentration among younger males.
Following the meeting, a draft CDC safety-monitoring report stated that “the signal for myocarditis that colleagues from Israel described should be further examined in U.S. safety monitoring systems.” Under “Future analyses requested,” it specifically called for myocarditis to be examined in other safety-monitoring systems, “based on data from Israel.”
By May 10, 2021, when the FDA expanded the emergency authorization of the Pfizer vaccine to adolescents aged 12-15, Israeli health authorities had warned the CDC and EMA of a myocarditis signal more than ten weeks earlier and had presented updated safety-monitoring data to CDC and FDA officials at VaST five weeks earlier. Yet US physicians would not receive formal CDC guidance on recognizing and reporting post-vaccination myocarditis until May 28, and the FDA warnings would come only in late June.
On June 23, ACIP formally reviewed the myocarditis signal and concluded that the benefits of mRNA vaccination continued to outweigh the risks, including among adolescents and young adults. Two days later, on June 25, the FDA modified the EUA fact sheets to include warnings about myocarditis and pericarditis, and the CDC developed educational materials for clinicians and patients.
Nearly four months had passed since the first documented warning. Throughout that period, serious cardiac events continued to be documented in the internal Ministry record, while physicians and the public had not yet been formally informed of the signal. In its July report, the CDC described the acute clinical course of reviewed cases as “generally mild.” Among 304 hospitalized patients with known outcomes, 95% had been discharged by the time of review, and no deaths had been reported. Many had experienced resolution of symptoms with conservative treatment.
By July, the institutional framing was clear: vaccine-associated myocarditis was rare, concentrated particularly among young males after the second dose, generally mild in its acute clinical course, and outweighed by the risks of Covid-19.
Was the Official Reassurance Justified?
In addition to analyzing the pharmacovigilance dataset, our study examined, step by step, the scientific evidence underlying that reassurance. The evidence we found painted a considerably more complicated picture.
One Hong Kong study, for example, found myocarditis after the second dose in roughly 1 in 2,700 male adolescents. The signal was concerning enough that, in September 2021, Hong Kong health authorities recommended that adolescents aged 12 to 17 receive only one dose of the Pfizer vaccine instead of two, explicitly citing the risk of myocarditis following the second dose.
The Israeli experience is particularly relevant to our analysis. Mevorach and colleagues, in a study that grew out of the Ministry of Health’s investigation and substantially overlapped with the material we examined, reported the highest risk among males aged 16-19, roughly one case in 6,600 after the second dose. But that study was designed specifically to identify clinically confirmed myocarditis and used a 21-day window. The 1-in-6,600 estimate therefore applied to that specific endpoint and follow-up period, rather than to cardiac events more broadly.
Even when we restricted the comparison to the same 21-day window, it contained 52 additional serious reports among males and 36 among females that were not included in the myocarditis analysis. In addition, about 12% of the myocarditis and pericarditis reports in the internal file occurred more than 21 days after vaccination, beyond the follow-up window used in some early studies. One such report involved an 18-year-old who was hospitalized with myocarditis 29 days after vaccination.
Our dataset itself was restricted to hospitalizations and deaths, and therefore could not capture subclinical myocardial injury or milder presentations. In a prospective study of 777 hospital employees, systematic biomarker testing after an mRNA-1273 booster identified vaccine-associated myocardial injury in 22 participants, or 2.8%, most without symptoms or a clinical diagnosis of myocarditis. These findings complicate any simple characterization of vaccine-associated cardiac injury as rare, because the observed frequency depends in part on what is being measured and how actively it is sought.
The claim that these cases were generally mild and transient also deserves scrutiny. Rapid clinical recovery does not necessarily mean that the heart itself has fully recovered. In a 2022 study of 16 adolescents with myopericarditis after the second Pfizer dose, all improved clinically, yet 11 still showed late gadolinium enhancement, an abnormal finding on cardiac MRI, three to eight months later. The long-term significance of those findings remains uncertain, but rapid clinical recovery did not establish that the cardiac injury itself was transient.
We also examined the logic behind the claim that Covid-19 was more dangerous to the heart than vaccination. Vaccination and infection were often presented as alternative risks, as though a person faced one or the other. But the vaccines did not reliably prevent infection, so a vaccinated person could be exposed to both risks. Presenting the comparison as a choice between the cardiac risk of vaccination and that of infection could therefore be misleading: it implicitly treated vaccination as though it removed the competing risk of infection, when in reality it could add a separate exposure to a risk that remained.
And several large studies directly challenge the claim that Covid-19 posed the greater cardiac threat. A large Israeli study of roughly 800,000 unvaccinated people found no increase in post-acute myocarditis or pericarditis following SARS-CoV-2 infection. A later British study of more than one million children and adolescents found no Covid-related deaths, fewer than seven Covid-related critical-care admissions, and documented myocarditis and pericarditis only in the vaccinated groups.
Some studies also classified myocarditis according to whichever event happened most recently, vaccination or a positive Covid test, potentially attributing a case to infection even when vaccination had occurred shortly beforehand. One such large observational study used this kind of exposure classification. And in a Nordic study of 23 million people, males aged 16-24 had 1.37 excess myocarditis cases per 100,000 after Covid-19 infection, compared with 5.55-18.39 after a second vaccine dose.
These findings challenge the institutional narrative that vaccine-associated myocarditis was rare, generally mild, and transient, and less concerning than the cardiac risks of Covid-19.
What Was at Stake?
By May 10, 2021, when the FDA expanded the emergency authorization of the Pfizer vaccine to adolescents aged 12-15, the myocarditis signal had been known for more than ten weeks, presented in updated Israeli safety-monitoring data to CDC and FDA officials, and flagged by the CDC for further examination. Yet US physicians would not receive formal CDC guidance until May 28, and the FDA warnings would come only in late June.
That timing was especially consequential. Vaccination was now being extended to younger adolescents, a population at very low baseline risk of severe Covid-19, but one in which the emerging cardiac signal was concentrated particularly among males. Parents and adolescents deciding whether to vaccinate needed to know what was already known, and what remained uncertain, about that risk.
If the signal warranted an active investigation and warnings to the CDC and EMA, and was subsequently flagged by the CDC for further examination, why did it not also warrant an early warning to physicians and the public?
The same delay also affected clinical recognition and reporting. Physicians who were not alerted might be less likely to connect chest pain or other symptoms with recent vaccination, investigate the possibility, or report the case. We cannot know how many cases might have been recognized earlier, or whether any hospitalizations or deaths could have been prevented. But one thing we can say with certainty: by May, before vaccination was expanded to younger adolescents, the cardiac safety signal was flashing red.
In risk communication, timing and framing are critical. Informed consent depends on how a known risk is presented. Yet when the risk was eventually communicated, it was framed as rare, generally mild, and outweighed by the risks of Covid-19, a reassurance that the broader evidence does not justify.
Meaningful informed consent also requires transparency about the evidence on which such reassurance is based. While Pfizer, a private pharmaceutical company, received detailed reports of hospitalizations and deaths, the underlying record was not made available for public or independent scrutiny. That is why we considered it essential to publish an anonymized version of the dataset, allowing others to examine the evidence for themselves.
Israel, the “world’s laboratory” of the vaccination campaign, sounded the warning by the end of February 2021. The CDC and EMA were warned. Pfizer received the detailed reports. Physicians and the public were left in the dark, never given the full picture. More than five years later, the record is finally public.
Original Author: Yaffa Shir-Raz | Source: Brownstone Institute
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