#DiedSuddenly Was Bullshit: So Why Did We Believe It?
Covid Vaccines did NOT lead to an increase in sudden death
I suppose, in retrospect, it was inevitable. The moment that covid vaccines were approved in what was an unprecedented scientific effort, the backlash began. There have always been vaccine skeptics, but this response was worse, fueled by suspicions that the work done to create these vaccines was somehow too fast, and turbocharged by the amplifying effect of social media.
There is a bit of a hack to getting your voice amplified on Twitter — now X — or Facebook, or any engagement-based platform: Inflame emotions. And few anti-vaccine trends were more powerful in 2021 than the one with this hashtag: #DiedSuddenly.
The stories were heartbreaking. Young people, healthy, struck down in the prime of their life, with no symptoms to speak of. One moment playing soccer or football, the next in cardiac arrest.
Source: X
If you were on social media at the time — you couldn’t get away from that hashtag. The implication — these deaths were due to vaccination — was ghoulish, but more ghoulish was the ravenous way the reports of virtually any death were quickly followed by a chorus of online voices asking whether the person was vaccinated or not.
Source: X
If your only access to information was via social media, you would have thought we were in the midst of a second epidemic. There was even a “documentary” made about the phenomenon, which streamed on Rumble and Twitter, and was promoted by Marjorie Taylor Greene.
Source: IMDB
Anti-vaxxers actually ended up opposing the film — saying it was so poorly researched it must have actually been a form of controlled opposition. But that’s neither here nor there.
This week, I’m going to show you a new study that confirms, in addition to studies that have already been released, that this #DiedSuddenly thing was, for lack of a better word, bullshit.
But I want to use it as a springboard to talk about just why a campaign like #DiedSuddenly was so effective, the errors in our cognitive processes that cause us to believe these things, or worse, share them online — and how we might avoid those traps in the future.
Let’s get one thing out of the way early. There was no increase in sudden cardiac arrest or sudden cardiac death among young people during the Covid pandemic. That is the conclusion of this study, appearing this week in JAMA Network Open, from Jonathan Drezner and colleagues at the University of Washington.
Source: Astley et al. JAMA Network Open 2025
To understand this study, you need to know that the National Center for Catastrophic Sports Injury Research keeps, and has kept since 2014, a database of virtually every cardiac arrest and sudden death that occurs among middle school, high school, and college athletes. This operates through active surveillance as well as direct reporting. In fact, researchers will track down social media reports of sudden cardiac arrests and deaths to add to the database if, for some reason, the NCAA did not report it.
In other words — this is pretty much the definitive count of these events in the United States over time.
So let me dispense with the prologue and show you the numbers.
In the three years prior to the pandemic, there were 203 cases of young athletes who suffered cardiac arrest or sudden cardiac death. In the first three years of the pandemic, there were 184 cases of young athletes who suffered cardiac arrest or sudden cardiac death. There is no statistical difference. There is no spike during the pandemic, either due to the covid virus itself or due to vaccines. There is simply no signal. This “phenomenon” was not real.
Source: Astley et al. JAMA Network Open 2025
This data adds to this study, appearing in Circulation, finding no association between vaccination and the risk of out-of-hospital cardiac arrest in the broader population in Australia. That’s that flat blue line despite the spike in infections and vaccinations that occur towards the end of the timeline.
That’s it. #DiedSuddenly was wrong.
So… why was it so compelling? Now that the panic of the pandemic has subsided, as has the use of that damnable hashtag, perhaps we can use our retrospectoscope to identify exactly why this idea had such a hold on people. It speaks to a number of well-described cognitive biases.
The first concept to be aware of is something called the illusion of truth effect. This is a well-described cognitive bias where we are more likely to believe something is true if we’ve heard it before, regardless of whether we believed it the first time around. It’s the simple power of repetition. You see something, you see it again, you see it again, you see it again, and it lodges in your brain.
This is a cognitive bias tailor made for social media. What is “going viral” beyond everyone repeating something you’ve tweeted or posted or whatever? Beyond that — social media algorithms, by their nature, show you things you’ve engaged with before — they keep ringing that bell, so to speak.
Let’s say the first time you saw a story of someone who died suddenly you were skeptical — you investigated and found, for example, that the story actually occurred prior to the pandemic — you are still more likely to believe the next “died suddenly” story. And the next one more so, and so on and so on. It’s just the way our minds work. This is the illusion of truth effect and it is very dangerous.
The second cognitive bias #DiedSuddenly exploits is known as the Affect Heuristic. This is a mental shortcut where we rely on our emotional response to something — our feelings — to make judgements about it, as opposed to facts. When a story elicits joy, or anger, or fear, or sadness, we are more likely to believe it is true. It’s the “shark attack” bias. Sure, we all know, rationally, that being killed by a shark is incredibly unlikely. But we hear a story about someone being killed by a shark and it changes our calculus about going into the ocean dramatically.
And finally, there is good old-fashioned motivated reasoning. This is when there is a conclusion we want to be true, we tend to believe facts in support of that conclusion and disregard facts to the contrary. Politicians are great at this, by the way. This is a huge problem when it comes to medical misinformation, because, again thanks to the internet, there are falsehoods out there that, if we choose to believe them, lead us to conclusions that are much better than reality. We may believe the falsehood that avoiding sugar cures cancer because of our fear of chemotherapy.
We may believe that a juice detox can “reset” our health because the reality of sustaining meaningful lifestyle change over time is simply too daunting. Or, in the case of a new vaccine that makes us nervous, we may embrace the excuse that people die suddenly from it to justify our reluctance to take it in a world where there are lots of pressures to take it.
Oh — and I almost forgot. There is always grifting. While I am sure that many people espousing this #DiedSuddenly nonsense were true believers, there were others trying to make money off of the fear. People sell merchandise with the hashtag. People offer online supplements to “detox” vaccines. People monetize their social media followers. They write books and charge subscriptions to newsletters. And no, I’m not going to link to any of these things. You can find them if you want.
So there you have it. COVID vaccines did not lead to a rash of sudden deaths in young athletes. COVID itself didn’t either. All the hype was just that — hype. And the reasons we believe it are as old as human psychology. May we be wiser next time.
A version of this commentary first appeared on Medscape.com.