Major COVID vaccine study finds heart risks are rare — and the real threat is being unvaccinated

Even while the COVID-19 vaccines have been hailed as one of the greatest achievements in modern science, they have been swirled in misinformation perpetuated by anti-vaccine figures and organizations who question their efficacy and robust safety record. The shots have even been wrongly blamed for high-profile health events, like when LeBron “Bronny” James Jr. suffered a cardiac arrest during practice. While research has shown that a COVID-19 infection is linked to an increased risk in myocarditis, which is inflammation of the heart muscle, how — and if — that translates to causation from vaccines has been widely taken out of context.

But now, a new study, published in the journal Vaccine, examined the potential health effects of the coronavirus vaccines. In its international attempt to separate fact from fiction, scientists have found that there are some links between the vaccines and adverse health effects to be aware of — but more research is needed to land on any definitive conclusions. 

“What we wanted to do was to see if there was any signal to suggest that COVID vaccines might be associated with an increased risk of certain medical events occurring,” Helen Petousis-Harris, a co-author of the study and co-director of the Global Vaccine Data Network, told Salon. “So what we did was we compared what we would normally expect to see — because these events occur all the time — what would you normally expect to see, and what are we actually seeing.”

The study included 99 million people across eight countries and found that the first, second and third doses of Pfizer-BioNTech’s and Moderna’s mRNA vaccines were linked to rare cases of myocarditis. Specifically, people who received a second dose of Moderna vaccine were 6.1 times more likely to have myocarditis. The condition also developed among people who received the Pfizer vaccine while researchers identified that pericarditis had a 6.9-fold increased risk for those who received a third dose of AstraZeneca’s vaccine.

There was also a 2.5-times increased risk of developing the rare autoimmune disorder called Guillain-Barré syndrome linked to those who received AstraZeneca’s vaccine. Separate research has found that COVID itself can cause this syndrome at a rate far higher than vaccines.

Petousis-Harris told Salon in general that the researchers weren’t surprised with the findings, in part because previous research had already pointed to the rare risk associated with vaccination and conditions like myocarditis and pericarditis. But they did pick up something that hadn’t been discussed before: a link between AstraZeneca’s viral-vector vaccine and acute disseminated encephalomyelitis, a rare condition that causes inflammation and swelling in the brain and spinal cord.

“And what that enabled was to take the next step, to a different kind of study, to really ask the question: Is this a problem?” she said. “Our colleagues in Australia performed a study in 6 million people, which is in the same issue, to look at that, and found that essentially after the viral-vector vaccines, the risk is about less than one extra case per million doses. So very very rare.” 

Notably, the risk was not observed in the mRNA vaccine design.

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As Salon has previously reported, COVID-19 vaccines changed the course of the pandemic. The mRNA technology, which was novel at the time, allowed for an effective vaccine to be developed in record time. Yet what the scientific community saw as a historic moment for biotechnology turned into a polarizing debate among American lawmakers who fell for conspiracy theories and misinformation surrounding the vaccines — marking a pivotal turning point for the anti-vaccine movement. Typically, misinformation about vaccines doesn’t appear out of nowhere. There is usually a kernel of truth to it, and the misinformation persists because it lacks context. 

Unsurprisingly, this study is already being used to justify long-held concerns about the vaccines. But experts say that doesn’t come as a shock and that misrepresenting this study doesn’t tell the whole story about weighing the risk between being unvaccinated and getting infected with COVID-19, and getting vaccinated against COVID-19. For example, previous research has found that the risk of myocarditis is seven times higher from getting a coronavirus infection than getting vaccinated. 

Glen Pyle, a molecular cardiologist who investigates cardiac injury associated with COVID-19, told Salon via email the most recent study is “a great example of the continuous safety monitoring that vaccines are subjected to, and it confirms much of the safety work already done.”

“For example, with adverse events like myocarditis it shows that these events are very rare,” he said. “And when we stack these rare risks up against the overwhelming cardiovascular benefits of vaccination, the case for vaccination becomes clear.”

Pyle added that this study highlights the need for public health experts to communicate the risks of vaccination and how common they are in the right context. 

“For example, myocarditis is a very rare complication that increases primarily in younger males,” he said. “On the other hand, cardiac arrhythmias are far more common and they increase significantly with infection, but not vaccination — in fact, vaccination decreases these risks.” 

He added there are “small but real increases in rare risks after vaccination, compared to large increases in very common risks with COVID-19.” 

This strengthens the case for vaccination, and why cardiovascular societies throughout the world recommend vaccination, especially for people with cardiovascular conditions. Petousis-Harris said it’s hard when a study like this is published because “risk communication” is a complex science on its own.

“You have lots of ways you need to communicate this, and I think it’s vital to be open and transparent with people, but you also have to work hard at how you are able to present to them,” she said. “I think it’s important to empower our people who are health professionals and vaccinators to be able to confidently have those conversations with people and have the tools that they need to help show people what the risks look like.”

She emphasized that any pharmaceutical has risk of side effects. 

“Probably vaccines are the safest of all pharmaceuticals by a longshot,” Petousis-Harris said. “One of the challenges is actually expressing how safe they really are. And another challenge is that we have health events happen by chance all the time, and they may or may not be related to a vaccine.”

She added that what has become clear is that it’s been difficult for people to grasp this nuance when it comes to the COVID-19 vaccines. 

“People are really interpreting anything bad that happens after the vaccine has therefore been caused by the vaccine,” Petousis-Harris said. Notably, the study only examines links and associations — potential “safety signals,” it’s not definitively declaring a cause. “Ultimately, if the issue is transparency, this is transparent.”