What We Know About Breakthrough Infections And Long COVID

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Weeks after getting sick from COVID-19, Kathleen Hipps is still experiencing symptoms, even though she was fully vaccinated. / Kathleen Hipps

Like millions of others, Kathleen Hipps thought she was safe from COVID-19 after she got two shots of the Moderna vaccine last spring. So she figured she just had a summer cold when she got the sniffles in July. But then she opened some Vick's VapoRub.

"Anyone who's ever smelled Vick's VapoRub knows how pungent of a smell it is. And I couldn't smell it. And that's how I knew I had COVID," says Hipps, 40, a Los Angeles lawyer who has two young sons.

And sure enough, Hipps tested positive. "I got very sick. I was very tired, very congested — could barely get out of bed. I couldn't work at all. I had to find colleagues to cover my work for me. And I just spent the next week basically in bed, completely isolated from my family," she says.

Hipps never ran a fever, though, and did not have bad head or body aches. She started feeling better after about a week, tested negative and went back to working from home and caring for her family. She thought she was fully recovered.

"And I was in my mom's new car and all of a sudden I felt burning. And I thought there was something wrong with her car," she says.

Wherever she moved her foot, she could still feel the burning sensation. And then her other foot started burning too. It felt like she was walking on hot coals, she says.

"I've learned that this is neuropathy, and this a common symptom of long COVID," Hipps says.

Some patients' symptoms last for weeks or months

Long COVID is a poorly defined, poorly understood condition that occurs when COVID-19 patients' symptoms won't go away for weeks or months, or new ones emerge just when they think they're all better.

More than six weeks after it started, Hipps still experiences the burning sensation every day, as well as tingling and numbness in her hands.

Sometimes the numbness is so bad she can't push her baby's stroller. Her periods are really heavy. And work tires her out so fast now that she has to take lots of breaks.

"I'm really scared. I mean I'm really scared that there are things that are going on with me that I'm going to have to deal with for the rest of my life," Hipps says.

Now it's really important to stress that the COVID-19 vaccines are still highly effective at protecting people from getting really sick or dying, and are still quite good at keeping most people from even catching the virus or getting mildly ill.

But breakthrough infections can happen, especially with the delta variant. And it's becoming increasingly clear that unvaccinated people can develop long COVID symptoms, even from mild cases.

"We've seen that with the infection itself in the unvaccinated individuals about 30% of those individuals continue to have these long-haul COVID symptoms," says Dr. Avindra Nath, who is studying long COVID at the National Institutes of Health.

So the concern is whether vaccinated people who get infected may be at risk for long COVID too, Nath says.

"I think that's a good question," he says.

Studies look for answers about long COVID

A small Israeli study recently provided the first evidence that breakthrough infections could lead to long COVID symptoms, although the numbers are small. Out of about 1,500 vaccinated health care workers, 39 got infected, and seven reported symptoms that lasted more than six weeks.

And a large British study subsequently found about 5% of people who got infected — even though they were fully vaccinated — experienced persistent symptoms, although the study also found that the odds of having symptoms for 28 days or more were halved by having two vaccine doses.

"I think it's a reasonable concern. But it's too early. I think we need to follow these patients. It's quite recent that they've been recognized. So at the moment we don't have that answer," Nath says, adding that if there is a risk, he suspects it's probably very low.

But the experts don't all agree

Some infectious disease experts remain highly skeptical that long COVID from breakthrough infections is a big problem.

"Pathophysiologically, it's quite unlikely to get long COVID from a breakthrough infection," says Dr. Monica Gandhi, an infectious disease researcher at the University of California, San Francisco.

That's because the immune response generated by the vaccine would prevent the virus from taking hold in the body or triggering a harmful overreaction by the immune system, Gandhi says.

"I think it is absolutely not impossible, but pathophysiologically it is less likely," she says.

Other researchers are convinced the problem is real.

"Categorically I can say that we have already been seeing a handful of cases of long COVID from breakthrough infection," says David Putrino, who studies long COVID at Mount Sinai.

"We need to behave as though there is the same chance as always of developing long COVID from a mild-to-asymptomatic infection because once you have it you can't unring that bell and you're looking at months to years of illness," Putrino says. Putrino is working with Akiko Iwasaki, an immunologist at Yale University, to try to understand how breakthrough infections can lead to persistent symptoms.

Iwasaki says some people may experience long COVID because the virus is still hiding in the body. In others, it may be that their immune systems overreact to the virus — a so-called autoimmune response.

"We know that the vaccine induces a robust immune response to quickly clear the virus during breakthrough infections," Iwasaki says. "And that suggests to me that autoimmunity may be the culprit there."

Even if breakthrough infections can lead to long COVID, others say there are also plenty of other reasons vaccinated people should continue to keep being careful to avoid catching the virus.

"At the end of the day, my biggest concern honestly is not that I'm going to get long COVID," says Dr. Carlos del Rio, an infectious disease researcher at Emory University. "It's that I'm going to bring COVID and give it to someone else. I mean, I have a young granddaughter. If I get infected, I could give it to her. I'm more concerned that people who are vaccinated can get infected and transmit to others."

For her part, Hipps hopes her symptoms don't plague her for months or even years.

"It's scary because there's obviously a lot of things we don't know about this virus and I'm scared about these long-term implications on my body."

Still, she is glad she got the vaccine. She knows it probably kept her out of the hospital and kept her alive.

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