This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven't subscribed yet, you can do that by clicking here.
An inaccurate Canadian study suggesting an extremely high rate of heart inflammation after COVID-19 vaccines has been retracted due to a major mathematical error — but not before it spread like wildfire on anti-vaccination websites and social media.
The preprint study, which was released by researchers at the Ottawa Heart Institute last week but has not been peer-reviewed, looked at the rate of myocarditis and pericarditis cases after Moderna and Pfizer-BioNTech vaccinations in Ottawa from June 1 to July 31.
The study identified 32 patients with the rare side effects out of a total of 32,379 doses of mRNA vaccines given in Ottawa in the two-month period, finding an inordinately high rate of close to 1 in 1,000 — significantly higher than other international data has shown.
But the researchers made a critical error that experts say caused the study to be "weaponized" by the anti-vaccination movement at a time when concern over COVID-19 vaccine side effects are top of mind for parents whose kids may soon get the shot.
Risk of heart inflammation after shot 'not correct' in study
The researchers mistakenly failed to record the accurate number of vaccinations given out during that two-month period, despite the data on total doses being publicly available, and the figure turned out to be astronomically higher than what was presented in the study.
Instead of 32,379 mRNA vaccine doses administered in June and July, as the study suggests, there were actually more than 800,000 shots given out at that time, according to Ottawa Public Health.
That means the true rate of side effects is closer to 1 in 25,000 — not 1 in 1,000.
"We recalculated the rate, and the rate is not correct in that paper," said Dr. Peter Liu, scientific director of the Ottawa Heart Institute and a co-author of the study, in an interview with CBC News.
"We were doing this on the run, in a way, and we were getting kind of the preliminary vaccination rate data, and so it turns out that that number was not complete."
Dr. Andrew Crean, co-director of the cardiac MRI service at the Ottawa Heart Institute and the study's lead author, confirmed to CBC News in an email Thursday that the preprint was being retracted.
Late Friday night, the study was officially marked as "withdrawn" on the medRxiv preprint server, with a link to a statement citing "a major underestimation" of the rate of occurrence.
"In order to avoid misleading either colleagues or the general public and press, we the authors unanimously wish to withdraw this paper on the grounds of incorrect incidence data," the statement read.
"We thank the many peer reviewers who went out of their way to contact us and point out our error. We apologize to anyone who may have been upset or disturbed by our report."
Crean said the authors uncovered the "significant error" days after posting it to the server, finding a "substantial overestimate" of the risk of heart inflammation after vaccination, then moved quickly to get the study withdrawn.
"As you know, preprints are not full peer-reviewed publications," he said. "The peer-review process worked quickly and efficiently to detect our error and we were happy to retract this data once the error was confirmed."
And Crean is absolutely right — this is exactly how the process is supposed to work.
Preprints are traditionally a way for academics to share early information on important subjects before the data is peer-reviewed and published, said Ivan Oransky, co-founder of Retraction Watch, a website that tracks errors in science journals.
"If in fact this is retracted quickly and withdrawn quickly based on what seems to be a pretty significant error, then it's actually science doing what it should," he said.
"The problem is not the preprint server, the problem is that nobody ever provides any context around it."
Side effect remains rare, treatable
The Ottawa Heart Institute issued a tweet late Wednesday night, a week after the study was released, saying the authors "have requested the retraction of the preprint" due to "incorrect data" that "vastly inflates the incidence of post-vaccine myocarditis."
"We are sorry a preprint paper citing incorrect data led to misinformation on the incidence of post-vaccine myocarditis," a spokesperson for the institute said in a followup statement to CBC News on Friday morning.
"COVID-19 vaccines are safe and have been proven effective against the disease. We invite anyone who has not yet received the shot to please get vaccinated."
While some real-world data has shown an increased risk of heart inflammation after COVID-19 vaccines among younger age groups, it's important to remember the side effect is rare.
"Even if you took the worst-case scenario, it doesn't happen in 99.9 per cent of cases," said Montreal cardiologist and epidemiologist Dr. Christopher Labos. "So the vast majority of people, even young people, are going to get vaccinated and not have an issue with myocarditis."
A small proportion of people who do experience the side effect will experience mild symptoms that are treatable without hospital care, Labos said, and don't appear to cause "any major heart damage."
![](https://thumbnails.cbc.ca/maven_legacy/thumbnails/260/843/mpx-birak-heart-inflammation.jpg?crop=1.777xh:h;*,*&downsize=510px:*%20510w")
"So it looks as if this is a relatively mild side effect that should not dissuade anybody from getting vaccinated," he said. "Because the benefits really outweigh the risks."
One study from Israel published in the New England Journal of Medicine earlier this month showed a slight increased risk of myocarditis after vaccination — but the researchers stressed that COVID-19 is more likely to cause the side effect than the shot.
Despite this reassuring conclusion, experts say the speed in which preliminary data is being uploaded, manipulated and disseminated in the pandemic means one error can cause a lot of damage.
"Mistakes happen; I have no major criticisms to level against anybody here. They did exactly what they're supposed to do: When you make a mistake — you fix it," said Labos.
"The real problem here is that I worry that people are going to keep using the wrong version of the study to advance their agenda."
Cherry-picking 'rotten' data
Despite not getting any mainstream media coverage in Canada or anywhere else at the time it was published, the study quickly spread around the world on social media and anti-vaccination websites, where it was incorrectly claimed as evidence of the damage COVID-19 vaccines cause.
The preprint has been shared on Twitter more than 11,000 times in the week since it's been published, according to Altmetric, a company that tracks where published research is posted online. That's in the top five per cent of all research it's ever tracked.
One particularly damaging tweet that gained a massive response came from Robert Malone, an infectious-disease researcher and accused spreader of anti-vaccination misinformation who calls himself the "inventor" of mRNA vaccines despite evidence to the contrary.
University of Ottawa Heart Institute Retrospective Study Finds 1 in 1,000 mRNA Vaccinations Leads to Myopericarditis<a href="https://t.co/tcRauKapjR">https://t.co/tcRauKapjR</a>
—@RWMaloneMD
The study also showed up on numerous anti-vaccination websites, misrepresented as evidence that the rate of myocarditis had been intentionally underestimated and that thousands of children could be at risk of heart failure after vaccination in the future.
Timothy Caulfield, Canada Research Chair in health law and policy at the University of Alberta who has studied the challenges with preprints in the pandemic, says the way in which the erroneous study has been shared widely online to promote an anti-vaccination agenda is "incredibly frustrating."
"First of all, the topic is so sensitive with parents, with young adults. When people are doing this risk-benefit calculus and they see a study like this, even if it just crosses their radar on social media, it can have an impact on their intentions," he said.
"So a mistake like this can do real, serious harm — and I think it probably already has, unfortunately."
The error highlights the challenges with preprints, Caulfield said. On the one hand, they can create an open dialogue with academics and get research into the public domain quickly on important topics, but on the other hand, they can do irreparable long-term damage.
"Preprints can quickly be weaponized by activists when the data seems to bolster their ideology, and they lend credibility to claims that might otherwise appear non-scientific," added Jonathan Jarry, a biological scientist with McGill University's Office for Science and Society in Montreal.
"And when a preprint gets retracted because it was fraudulent or just simply incorrect, that bell is hard to un-ring in the public square that is the internet."
![](https://thumbnails.cbc.ca/maven_legacy/thumbnails/462/679/COVID-VACCINE-KIDS-HEART-BIRAK-040621.jpg?crop=1.777xh:h;*,*&downsize=510px:*%20510w")
Caulfield said that once an inaccurate preprint gets released, it can "take on a life of its own."
"And that's exactly what has happened here," he said. "I can guarantee that you are going to continue to see references to this version of the paper for a long time to come."
These so-called "zombie papers" are often intentionally shared within anti-vaccination circles long after they're retracted or corrected in order to disingenuously influence public opinion and fuel misinformation, said Caulfield.
"It's extreme cherry-picking," he said. "And the cherry is rotten."
A Canadian COVID-19 study that turned out to be wrong has spread like wildfire among anti-vaxxers - CBC.ca
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