Brittany Underwood was 37 when she was hit with COVID early in 2021. Her case was mild, and, like the mom she is, she took care of everyone else because of course the rest of her family had it too. It wasn’t until a couple weeks later that she started to feel lousy—wiped out, constantly thirsty, and dealing with weird issues like blurry vision in one eye.
When Underwood brought those symptoms to her doctor, he decided to run some blood tests. “My blood sugar was through the roof,” Underwood tells SELF. It was so high, in fact, she ended up in the hospital that same day, where they handed her a diagnosis that would change her life: type 1 diabetes.
This autoimmune disease is most often diagnosed by the age of 14—it used to be known as juvenile diabetes because it’s the type that most often hits kids, teens, and young adults. Because Underwood was approaching 40, her case was unusual. But her doctors raised a possible explanation: She’d just had COVID, and they suspected the infection might have triggered her diabetes.
Nearly four years later, we have a lot more than suspicions. In fact, the pandemic has been blamed for a spike in type 1 diabetes. New cases in kids and teens jumped up 16% in the first 12 months of the pandemic and 28% in the following year. (Before 2020, the typical increase was 2% to 3% per year.) And it’s not just type 1. Other autoimmune diseases—including rheumatoid arthritis (RA), psoriasis, and lupus—went up too. Exactly why that happens isn’t fully clear, Sonia Sharma, PhD, an associate professor at La Jolla Institute for Immunology, in La Jolla, California, tells SELF. “But,” she adds, “we do have some clues.”
When your immune system turns on you
The idea that COVID could set off a chronic autoimmune disease might seem out there. But, Dr. Sharma says, “it’s not a new concept at all.” Autoimmune diseases are caused by a misguided immune system attack on the body’s own healthy tissue. For that to happen, a perfect storm of conditions has to come together. Genes definitely matter, Dr. Sharma says, since autoimmune diseases tend to run in families, and studies have tied certain genes to higher risks of the conditions. (Underwood says she has a family history of autoimmune diseases.) Your sex assigned at birth matters too: Autoimmune diseases are way more common in women than men, Dr. Sharma notes (though anyone can get them).
But those kinds of risk factors aren’t enough on their own. People have to be exposed to one or more “triggers” that tip the immune system into self-attack mode. And microbes are among those potential sparks, Akiko Iwasaki, PhD, professor of immunobiology at Yale School of Medicine, tells SELF.
Studies have linked a slew of infections—including super-common ones like the flu, cytomegalovirus, and Epstein-Barr virus—to various autoimmune diseases. Epstein-Barr, which eventually infects nearly everyone and is usually no big deal, may be the prime example: A recent study found that the infection likely plays a role in most cases of multiple sclerosis (an autoimmune disease that destroys the protective covering around nerve fibers).
There are different theories on exactly how it happens, but Dr. Iwasaki offers a (relatively) basic overview. First, she says, it’s a little known fact that everybody has some number of immune system cells that are “autoreactive,” meaning they’re capable of going rogue against you. Thankfully, they usually don’t. But in certain people, under certain circumstances, an infection might “activate” those autoreactive immune cells.
“Once they’re activated,” Dr. Iwasaki explains, “they can divide and travel to different tissues in the body, and may start to attack your own cells.” All of that, she adds, is more likely to happen when an infection generates lots of inflammation in the body. An ordinary cold probably won’t do that, but COVID might.
How big is the risk?
Even though it can seem like we’ve been living with COVID forever, it’s still a very new thing. Because of that, Dr. Sharma says, it’s only recently that studies have been able to turn up strong evidence that the infection does trigger autoimmune diseases.
That includes this 2023 study of close to 4 million Americans. It found that people diagnosed with COVID had higher odds of developing autoimmune diseases over the next six months, versus COVID-free people. On average, they were roughly three times more likely to be diagnosed with conditions like RA, lupus, psoriasis, celiac disease, and type 1 diabetes.
Really important to point out here: Although three times more likely might sound huge, the risk of any one person developing an autoimmune disease after COVID is still low, Sara Martin, MD, medical director of Vanderbilt University Medical Center’s Adult Post-Acute COVID Clinic, in Nashville, tells SELF.
Another 2023 study, published in Clinical Rheumatology, helps put things into context. It found that of 565,000 people with COVID and no history of autoimmune disease, 1% were diagnosed with an autoimmune condition over the next 3 to 15 months. That was 43% higher than the rate among people who didn’t have COVID during the same period. Although that sounds like a lot, it was an increase from roughly 11 to 15 cases per 1,000 people per year. So…not a huge amount, but not something to dismiss either. And if you’re one of the unlucky people who does develop an autoimmune condition, that’s a heavy toll.
“All of a sudden I had this huge life-altering thing,” Underwood says of her diabetes diagnosis. People with type 1 have to take insulin injections every day to stay alive. So Underwood was forced to quickly learn the intricacies of carb counting, adjusting insulin doses, timing meals to avoid dangerous blood sugar drops—and managing them when they did happen. Time and experience, as well as connecting with other people with type 1 diabetes, have taught Underwood a lot. “But I’m still learning, three years later,” she says. “It’s just a constant thing. You can’t take a day off.”
Is there a way to protect yourself?
At this point, many of us have had COVID more times than we’d prefer. So does your immune system get used to the virus, and maybe make an autoimmune reaction less likely?
Unfortunately, Dr. Iwasaki says, there’s reason to believe the answer is no. That’s based on what researchers have learned about long COVID, a collection of symptoms like extreme fatigue and brain fog that hits many people post-infection. Prior bouts of COVID do not seem to lower the odds of developing long COVID (and the risk might even go up each time you’re infected). Long COVID, Dr. Iwasaki notes, is different from autoimmune diseases like type 1 diabetes and RA because the cause isn’t clear and may be due in part to direct damage caused by the virus. But she and other researchers have found that autoimmune reactions to COVID infection may also be behind long COVID symptoms, at least in some people. “I think that’s one clue that reinfection would not lower the risk of autoimmune disease,” Dr. Iwasaki says.
Okay, now for the good news: COVID vaccination might be protective. For one, Dr. Martin says, research shows that vaccination can lower the risk of long COVID, and the more vaccine doses you get, the greater the protection.
There’s also this large study published last year by researchers in China, which found that although COVID was associated with an increase in many autoimmune conditions, those risks were lower among people who’d gotten at least two COVID vaccine doses, versus unvaccinated people.
It’s “absolutely” plausible that vaccination helps, Dr. Sharma says. Vaccination, she explains, primes your immune system to stop the COVID virus “at the front door”—your respiratory tract—so that it can’t hitch a ride around the body, churning up inflammation and, potentially, an autoimmune reaction. And while people can develop autoimmune disease after a mild case of COVID (as Underwood did), research suggests that the odds might be substantially greater if you become severely ill.
“We already recommend vaccination for everyone,” Dr. Martin points out. “It reduces the potential for severe COVID, and we know it also reduces the risk of long COVID.” If you’re worried about autoimmune disease (say, because you have a family history of them), Dr. Martin says that’s one more reason to stay up-to-date on your COVID shots.
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