Researchers discovered that about 1 in 35 health care workers at a Swiss hospital who received the mRNA-1273 vaccine had signs of heart injury linked to it. Normally, this level would only be around 1 percent in a healthy population.
According to the study, which was published in the European Journal of Heart Failure, “mRNA-1273 booster vaccination-associated elevation of markers of myocardial injury occurred in about one out of 35 persons (2.8%), a greater incidence than estimated in meta-analyses of hospitalized cases with myocarditis (estimated incidence 0.0035%) after the second vaccination.”
Even after 30 days of observation, half of the group experiencing these negative effects still had higher levels of high-sensitivity cardiac troponin T, which indicates hidden heart damage.
Because there hasn’t been much research following people with heart injuries after messenger RNA vaccination, which is known to cause heart problems like myocarditis, the study’s long-term implications are not clear yet.
“According to current knowledge, the cardiac muscle can’t regenerate, or only to a very limited degree at best. So it’s possible that repeated booster vaccinations every year could cause moderate damage to the heart muscle cells,” said University Hospital Basel professor Christian Muller, a cardiologist and the study’s lead author, in a statement.
Within a month of getting the booster shot, none of the patients had a major heart problem like heart failure, and their heart readings on the electrocardiogram were normal.
The researchers suggested that those with higher levels of heart markers were told to avoid intense physical activity, which might have helped prevent more serious issues.
Despite cardiologists recommending heart scans for suspected vaccine-related heart inflammation, the participants didn’t undergo any imaging to check their hearts.
Dr. Andrew Bostom, a heart specialist in the United States who wasn’t part of the study, mentioned that if imaging had been done, it could have shown inflammation that leads to scarring or an irregular heartbeat.
The findings, according to Dr. Anish Koka, an American cardiologist, were “super useful to see how ‘cardioactive’ the booster is,” but it was difficult to assess how significant the higher troponin levels were, especially without a comparison to baseline levels. “There is really nothing clinically concerning at 30 days to report,” he tweeted.
Study Methods
The researchers suggested that more cases of vaccine-related heart damage could exist after messenger RNA booster shots than we initially thought. This could be due to people not showing noticeable symptoms or only having mild symptoms.
They defined “injury” as a significant rise in high-sensitivity cardiac troponin T three days after the vaccine, with no other apparent cause. The cardiac troponin levels had to reach a certain upper limit: 8.9 nanograms per liter for women and 15.5 nanograms per liter for men.
At the University Hospital Basel, all staff set to receive their first Moderna booster were invited to join the study unless they had a heart event or surgery within a month of getting vaccinated. The boosters, given from December 10, 2021, to February 10, 2022, were half the strength of the initial shots. The study involved 777 participants, including 540 women, with a median age of 37 years.
Out of the participants, 40 had higher levels of cardiac troponin. Among them, 18 had other reasons for this elevation. However, the researchers identified “vaccine-associated myocardial injury” in the remaining 22. This group had a median age of 46, and nearly all were women. This contrasts with most earlier research on vaccine-linked heart inflammation, which often affected more men. The researchers explained that this might be because women received a slightly larger vaccine dose per kilogram of body weight.
Baseline levels were not taken because the study should “interfere as little as possible with the motivation of the hospital staff to obtain the mRNA-1273 first booster vaccination and the logistics of booster vaccination itself,” according to the hospital’s COVID-19 task committee and the researchers.
None of the individuals with higher markers had a history of heart disease. While half had symptoms, most were non-specific, like a fever. Two participants experienced chest pain. According to the Brighton Collaboration case definition, two likely had myocarditis.
The choice to test high-sensitivity cardiac troponin T was due to its sensitivity.
“This marker is extremely sensitive—with other methods such as MRI, we wouldn’t have been able to detect any damage to the cardiac muscle, as it only becomes visible once the damage there is about three to five times greater,” Dr. Muller said.
The researchers couldn’t determine how the vaccine might harm the heart muscle.
The authors disclosed some potential conflicts of interest, including Dr. Muller’s grants from drug companies like Novartis and Roche. The University of Basel and the University Hospital Basel funded the study.
Limitations encompass the absence of initial levels and imaging.
Previous Findings, and Pending Study
Multiple other studies have investigated myocarditis cases after Pfizer vaccinations.
In Thailand, among 301 teenagers, 29 percent showed cardiovascular effects like chest pain after the second Pfizer shot. Seven of them were diagnosed with heart inflammation.
In Taiwan, researchers checked the initial electrocardiogram readings before the second Pfizer dose and found abnormal results in one percent of 4,928 primary school students after the shot. This group included five students diagnosed with myocarditis or irregular heartbeats.
An Israeli study followed 324 health care workers, mostly around 51 years old, who received a second Pfizer booster. Two cases of vaccine-related heart injury were identified on the third day.
Recent studies have also confirmed fatal cases of vaccine-induced myocarditis. A South Korean study investigated eight sudden deaths after mRNA vaccination, ruling out other possible causes. Researchers hadn’t suspected myocarditis as a reason for these deaths before conducting autopsies.
The Swiss researchers emphasized the need for more studies to investigate heart injuries after vaccination. They also highlighted that the long-term consequences of these injuries are not yet clear.
U.S. authorities mandated Moderna to carry out a study to examine the occurrence of subclinical myocarditis after a booster among adults. The study was expected to be finished by June 30, 2023. However, neither the U.S. Food and Drug Administration (FDA) nor Moderna have revealed the study results so far.
Pfizer was also required to conduct a similar study, with the results originally due by December 31, 2022. However, the FDA extended the deadline at Pfizer’s request.
Meanwhile, the US government has now invested nearly $6 billion in an effort led by President Biden to provide a lifeline to Moderna amid the COVID-19 crisis.
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