SAN FRANCISCO CHRONICLE
My husband can’t watch soccer games anymore, and for a year I wondered if the COVID-19 vaccine was to blame.
His first stroke happened a few days after a COVID vaccination. It flummoxed everyone: He had no previous health problems, and the vaccine he got wasn’t associated with stroke. As a health researcher and vaccine proponent, I had a hard time making sense of it.
Now, at just 47, he has survived two strokes and lives with a constellation of small, weird brain impairments. For some reason, watching soccer players zip around the field blows some mysterious circuitry that rerouted to fix his post-stroke double vision.
When his first stroke happened, my husband and I thought we’d never understand why. Still, we got our young sons vaccinated, despite our uncertainty. Since then, I’ve heard from anti-vaxxers who think my husband and I deserve a fiery death for that decision. I’ve also heard from other young stroke victims who reached out to us looking for answers. It took time, but those answers are finally within our grasp, and they aren’t what we expected.
Our road to the truth began when my husband’s recovery suddenly took a turn for the worse; I found him lying on the concrete with his eyes closed at a Halloween party. A brain MRI later showed he had experienced a second small stroke.
This led to a fresh round of tests and eventually a formal diagnosis: antiphospholipid syndrome, or APS. It’s an autoimmune disease in which the immune system mistakenly makes antibodies that cause blood clots to form. APS is rare and can be hard to diagnose, but if you have a stroke before age 50, there’s a 20% to 30% chance you have it.
His diagnosis has been like strapping on a headlamp in the woods at night: Things are still dark, but at least we can see where we’re heading.
He’s on blood thinners to prevent further strokes and learning what triggers his symptoms and what activities are worth enduring them (Irish punk band on St. Patty’s Day, yes; packing suitcases on the floor, no). He finally got a COVID vaccine booster and sailed through it. It turns out that a COVID infection raises your risk of stroke, so we’re grateful he has that protection.
Doctors call the often-lengthy journey to diagnosing a rare disease a “diagnostic odyssey.” That epic quest is what happens when the human thirst for understanding collides with the need to make important life decisions. When it comes to our health, we need uncertainty resolved. But how we go about doing that can be deeply problematic.
Human brains tend to latch on to heuristics — decision-making shortcuts that simplify things, often in misleading ways. If one thing immediately follows another, for example, we assume they’re related.
One famous heuristic is Occam’s Razor: the idea that other things being equal, the simplest explanation tends to be the right one. The problem is that what’s simplest depends on the available information. Making matters worse, other heuristics can cause us to ignore information that’s right in front of us. Confirmation bias, for instance, leads us to filter out or downplay new information that doesn’t fit with our prior judgments.
Autoimmune diseases run in my husband’s family. With hindsight, that’s the simplest explanation for what happened. But in the days following his vaccination, we couldn’t see it.
In order to resist heuristics and make sound decisions, we have to be willing to recalibrate our judgment as the evidence evolves. When it comes to health matters, people really hate that.
It’s frustrating to be told, “Don’t worry about wearing masks — wait, no, definitely wear a mask!” My husband rolls his eyes whenever I mention new research on a healthy diet, preferring not to knock himself out making changes until next year when some new study recommends something different.
Maddeningly, that’s how science works. The knowledge landscape is always changing. Making decisions “based on the science” isn’t a one-and-done thing; it’s a commitment to always being on the lookout for new evidence and truly staying open to what it has to tell you.
Sometimes that message is hard to figure out. A few months ago the Centers for Disease Control and Prevention issued an alert about a possible “signal” that the COVID vaccine my husband took might be associated with a higher risk of ischemic stroke in older people. What were we supposed to do with that? Answer: keep listening. The CDC’s subsequent investigation and independent research showed the signal was a phantom; there wasn’t an association after all.
In the case of vaccines, a lot of people seem to have quit listening. Although certainty about the safety of COVID vaccines has increased as studies have accumulated (including studies in children ), COVID vaccination rates have plateaued. Now, the uptake of other childhood vaccines has slipped. Vaccine misinformation swirling around the internet makes forgoing those vaccines seem like the safer bet, but doctors view it as a slow-motion disaster.
I often think about a soft-spoken pediatrician I taught, Dr. Panda, whose voice grows forceful when talking about a young patient’s death from a vaccine-preventable disease. When counseling vaccine-hesitant parents, she hopes that if all the data she has to share about vaccine safety doesn’t move them, her story of the lost child will.
The simplest explanation may often be the right one, but it can also be tragically wrong.
Michelle Mello is a professor of health policy at Stanford University School of Medicine and a professor of law at Stanford Law School.