• Health

Swiss study doesn’t show that Moderna COVID-19 mRNA vaccine is dangerous for the heart, John Campbell and The Gateway Pundit exaggerated the study’s conclusions

Posted on:  2023-08-08

Key takeaway

A study by a research team in Switzerland found possible signs of mild and transient damage to cardiac cells following vaccination, but didn’t find evidence of abnormal heart function or myocarditis. Getting COVID-19 is associated with a higher risk of cardiovascular complications than vaccination, and the outcomes are worse. COVID-19 vaccines are safe and effective at reducing the risks of severe forms of the disease, including serious cardiovascular issues.

Reviewed content


“1 in 35 people showed signs of heart damage after taking the Moderna COVID19 vaccine”; it is a “kill shot”; taking “this kind of risk, it’s just complete madness”

Source: YouTube, Gateway Pundit, Jim Hoft, John Campbell, 2023-07-26

Verdict detail

Overstates the scientific impact of a finding: The claim exaggerated the clinical significance of the elevated troponin levels in the blood of some mRNA vaccine recipients. This elevation was actually transient, mild, and in the range of what intense exercise can produce. Furthermore, the study reported no abnormalities in heart imaging or electrocardiogram.
Lack of context: Cardiovascular complications are actually more likely and worse following COVID-19 than following vaccination. However, the claim by Campbell and the Gateway Pundit didn’t provide this information needed to place vaccine risk in context.

Full Claim

“1 in 35 people showed signs of heart damage after taking the Moderna COVID19 vaccine”; it is a “kill shot”; “this is a range of adverse reaction that is off the scale in healthcare”; taking “this kind of risk, it’s just complete madness”


A research team led by cardiologist Christian Mueller published a study in July 2023 investigating the effects of the Moderna mRNA COVID-19 booster vaccination on the heart[1]. Soon after the study’s publication, posts on social media circulated claiming that the study had revealed that mRNA vaccines were damaging people’s hearts.

It’s not the first time this research team’s findings have been used as a basis for misinformation. Similar posts occurred after Mueller presented the team’s main findings in 2022 at a scientific conference. Health Feedback explained why those posts were erroneous in a previous review.

Of the now-published study, the Gateway Pundit said that “1 in 35 people showed signs of heart damage after taking the Moderna COVID19 vaccine” and called it a “kill shot”. The Pundit added that “They forced Americans to take this vaccine to work and attend public events”, implying that vaccine mandates combined with the use of mRNA vaccines had put people at risk.

YouTuber and retired nurse instructor John Campbell also claimed that the study had identified an “off the scale” rate of vaccine-associated heart injury, repeating the “1 in 35” figure at length and describing this finding as “astounding”. He also commented that “we just don’t take this kind of risk, it’s just complete madness”.

Overall, such language gave the impression that the study showed that COVID-19 mRNA vaccines would lead to serious heart problems and placed people at an unnecessary risk.

Both the Gateway Pundit and Campbell have previously spread COVID-19 and vaccine disinformation, as we and others established on multiple occasions.

What the study did

To understand why these claims are misleading, we must first understand what the study did. The research team recruited volunteers who were planning to receive a third dose of Moderna mRNA vaccine (booster dose). The researchers excluded from the study people who had a cardiac event or surgery the month before. This is because these people are already likely to show signs of heart damage for reasons unrelated to the vaccine.

The researchers then measured the amount of high-sensitivity cardiac troponin T (hs-cTnT) in the volunteers’ blood three days after vaccination. Hs-cTnT is a protein present within the cells of the heart. When heart cells develop physical damage, even mild damage, some cells may rupture and release hs-cTnT into the blood. An elevated amount of hs-cTnT in the blood may thus indicate a possible heart injury.

From the total number of participants with elevated hs-cTnT, the researchers excluded those where an explanation other than vaccination was likely. For example, they excluded cases where a participant had a stably elevated hs-cTnT, indicating a possible chronic heart condition, or those whose preexisting troponin level was just slightly above the normal range.

This left 2.8% participants without other clear explanation for their elevated hs-cTnT than the fact that they had a booster shot. The researchers concluded from that that these people had a mRNA vaccine-associated heart injury. This is where the “1 in 35” figure repeated by the Gateway Pundit and Campbell comes from—2.8% is equivalent to 1 in 35.

Levels of hs-TnTc are only moderately and transiently elevated, the clinical relevance is debatable

The “1 in 35” figure is thus accurate. The problem is that Campbell and the Gateway Pundit’s coverage overlooked the study’s limitations and exaggerated the significance of this figure.

First, the researchers didn’t measure the baseline level of hs-cTnT before vaccination. Even though they took care to exclude participants whose elevated troponin could be explained by something other than the vaccine, we still don’t know whether all the remaining participants had pre-vaccination troponin levels within the normal range. Some of them may have a higher than normal level of hs-cTnT for whichever reason and would be erroneously counted among the 2.8%.

Second, the elevation of troponin levels was only moderate and transient. Some of those who propagated the claim, like Campbell or the Gateway Pundit, did acknowledge this, but glossed over it and didn’t include it when assessing the importance of that finding. This is problematic because such a moderate increase might not be of much clinical significance, according to some experts.

Cardiologist Anish Koka explained on Twitter that the level of troponin was actually close to what is considered a normal level.

James de Lemos, a cardiology professor at the University of Texas, told Lead Stories that “these small troponin elevations are not likely events of clinical significance”.

Lead Stories also talked to William Schaffner, a professor of health policy at Vanderbilt University, who emphasized that the troponin elevation was “mild, temporary and totally without symptoms”.

In a similar vein, James Lawler, a professor in the division of infectious diseases of the University of Nebraska, told Lead Stories that “All of these were mild elevations […] and most seemed to revert to normal quickly”.

In fact, hs-cTnT can rise to a similar level even after normal physical activity, like intensive exercise, as scientist Susan Oliver pointed out in her review of Campbell’s video. A meta-analysis of studies on troponin levels during physical activity found that endurance exercise increased the level of hs-cTnT by an average of 26 ng/L[2]. After an intense swimming exercise, hs-cTnT peaked between 11.9 and 22.7 ng/L in teenagers and adults[3]. Similarly, the median level of hs-cTnT rose to 21 ng/L in adults and children hours after having played football (soccer)[4].

By comparison, the hs-cTnT level was only 5 ng/L among the participants in the study, and reached 13.5 ng/mL among the 2.8% who may have had a mRNA vaccine-associated heart injury.

Therefore, the level of troponin after vaccination is no higher, and sometimes even lower, than what could occur after an intense physical activity. Furthermore, the levels of hs-cTnT fell rapidly. Half of the participants with elevated levels at day three were already back to normal levels at day four.

As explained, elevated troponin can indicate damage to the heart cells. So it is important to directly examine the heart, using imaging or electrocardiogram (ECG) to check whether the heart is working properly. The study did just that and found that none of the participants had alterations in their ECG, and no definitive cases of myocarditis were found. Upon the follow-up at thirty days post-vaccination, none of them showed any major cardiac adverse events.

Therefore, there were no detectable or lasting cardiac consequences from COVID-19 mRNA vaccination. Proponents of the claim like Campbell and the Gateway Pundit promoted a dire account of the study’s results on elevated hs-cTnT that ignored the other results indicating no lasting changes to heart function. By doing so, they conveyed a distorted and exaggerated vision of the study’s message.

In a further misrepresentation of the study’s results, the Gateway Pundit also inaccurately claimed that the level of troponin was still above normal in half the participants one month later. In fact, the study didn’t perform any hs-cTnT measurement at one month post-vaccination, and as explained above, half the participants had already shown normal troponin levels by day four post-vaccination.

Similarly, Campbell claimed that people who had done strenuous exercise were excluded from the study beforehand. This is also false. While none of the participants reported such exercise, this wasn’t an exclusion criterion in the study.

COVID-19 is more likely cause serious cardiovascular problems compared to COVID-19 vaccination

Not only did the claim exaggerate the significance of the elevated hs-cTnT reported in the study, but it also failed to put these results in perspective with the risks of COVID-19 itself.

The study acknowledged that “COVID-19 associates with a substantially higher risk for myocarditis than mRNA vaccination, and myocarditis related to COVID-19 infection has shown a higher mortality than myocarditis related to mRNA-vaccination”[1,5,6]. Indeed, contrary to the COVID-19 mRNA vaccines, COVID-19 can cause severe cardiovascular problems and is more likely to cause such problems[7,8].

Therefore, while the COVID-19 mRNA vaccines may cause mild and transient injury in heart cells, it reduces the risk of serious and possibly fatal cardiovascular complications from COVID-19. This is an important piece of information, necessary to fully assess the risk-benefit ratio of vaccination, that the claim overlooked. On balance, the benefits of COVID-19 vaccination outweigh its risks.


The study by Mueller and his team offers new information on the effect of mRNA vaccination on the heart. They found that booster shots caused a mild increase in hs-cTnT that could indicate transient and moderate damage to the cardiac cells.

However, the levels of elevated troponin observed in the study are moderate, similar to what can be observed after an intense exercise and may not be of clinical significance. The researchers also used direct methods of examining heart function, such as medical imaging and electrocardiograms, and didn’t detect any heart issues among vaccine recipients.

Therefore, those who framed the study as showing that COVID-19 mRNA vaccines were causing unexpected and dangerous damage to people’s hearts are exaggerating the results. As Mueller told Lead Stories: “Unfortunately, even now in Summer 2023 it seems difficult to have a balanced discussion on this side effect [myocardial injury]. Some people as [Campbell] massively exaggerate, others completely ignore it”.


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