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  • Estimates suggest that between 20 to 80 percent of people who contracted SARS-CoV-2 developed long COVID-19 symptoms.
  • Because long COVID can occur after milder cases, some people suspect breakthrough cases in vaccinated people could lead to long-haul symptoms, too.
  • A poll from a long COVID-19 advocacy group found some vaccinated people who developed COVID-19 went on to have symptoms of long COVID-19.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 pandemic.

For many diagnosed with COVID-19, the battle doesn’t end when they no longer test positive.

After the infection clears, the damage inflicted by the coronavirus — on the lungs, the heart, and brain — begins to become apparent. The symptoms associated with long COVID-19 vary from by person and can include:

  • chronic fatigue
  • breathing problems
  • brain fog
  • heart palpitations
  • dizziness
  • lightheadedness

Estimates from the United Kingdom suggest that between 20 to 80 percent of people who contract SARS-CoV-2 develop long COVID-19, otherwise known as long-haul COVID-19 or post-acute sequelae of COVID-19 (PASC).

But it’s largely unclear just how many people experience long COVID-19, what causes it, and how long the condition lasts. Some researchers suspect long-haul COVID-19 may be far more common than we think.

There’s also a chance we could be missing long COVID-19 in vaccinated people who develop breakthrough cases, too.

A recent poll from the nonprofit Survivor Corps, which focuses on advocating for people with long COVID-19, suggests that a small portion of vaccinated people who are diagnosed with breakthrough cases develop long-haul symptoms, too.

Health experts say we don’t have enough data to understand the risk of long-haul COVID in vaccinated people who develop the disease.

Dr. Linda Geng, the co-director of the Stanford Medicine COVID clinic, told Healthline there’s a wide range of post-COVID symptoms and severity.

The definition of what constitutes PASC is dynamic, making diagnosing the condition somewhat of a moving target, says Geng.

On one end of the spectrum, long COVID-19 symptoms are so bothersome and severe that they impact people’s daily functioning and activities. On the other end of the spectrum, some people develop milder symptoms that don’t disrupt their daily lives.

Other people “have mild symptoms that they might not even bring to the attention of their clinicians or their primary care doctors. It may just be something that they’re living with,” says Geng.

Furthermore, some patients may not even recognize their symptoms as a post-COVID-19 condition. Their joints may ache, their sleep may be disrupted, but they may not connect it to their illness, according to Geng.

“It’s likely under-recognized because A, there are probably underdiagnosed COVID cases. And then B, those who have had COVID, there are probably under-recognized symptoms that are actually linked with COVID and may not be brought up to their doctors,” Geng told Healthline.

And while we know the vaccines significantly cut your risk of developing COVID-19, it’s unclear how the shots impact a person’s odds of developing long-haul symptoms if they do get a breakthrough case.

“If you do get COVID after vaccination, the likelihood of developing severe COVID illness is far lower. But at the same time, the potential to develop long COVID symptoms in that context, we just don’t have enough data,’ says Dr. Hyung Chun, a Yale Medicine cardiologist and associate professor of medicine at Yale School of Medicine.

Chun says that, in general, long COVID-19 cases are less well-documented in the United States than in the United Kingdom.

“The U.K., because of their nationalized health system, they’ve been tracking this far more closely than we have,” Chun said.

In the United Kingdom, over half of the people who’ve developed COVID-19 are reporting some long COVID-19 symptoms, says Chun.

One of the many mysteries surrounding long COVID-19 is what causes the condition.

Chun says the current belief is that it’s caused by a combination of widespread inflammation along with injury to the organs.

Research has found that levels of inflammatory markers in blood correlate to how severe the disease was, suggesting that more serious cases are more likely to lead to inflammation that could cause lingering symptoms.

While it appears that more severe cases are more likely to lead to long-haul symptoms, even people who had mild COVID-19 cases experience lasting effects.

“We certainly do see patients who have had milder forms of COVID infection who do present with long COVID symptoms,” says Chun.

There is a chance that even milder breakthrough infections could lead to lingering symptoms, but more data is needed to understand the link better.

There’s a good body of research that suggests a high prevalence of long COVID-19.

According to Geng, studies conducted at Stanford have found that up to 70 percent of people diagnosed with COVID-19 had symptoms lingering beyond a month.

Longer-term studies evaluating patients at the 6-month mark and beyond have found that number to be closer to 40 percent.

“The question is how severe those symptoms are,” Geng said. Some patients have severe, debilitating symptoms, others have milder, more tolerable symptoms that can go untreated.

It’s also unclear what percentage of people seek medical treatment for their long COVID-19 symptoms.

“In terms of who actually seeks medical care for this, I think that’s an important question that we just don’t know,” says Chun.

Those with severe symptoms may check into a long COVID-19 clinic, but others may just learn to live with their symptoms.

There’s a lot we don’t know about long COVID-19. It’s difficult to track, and our ability to manage it is limited by our understanding.

“There are so many variables that we just don’t know, and we may not be able to fully capture that limits our ability to better understand the extent of this problem,” Chun said.

Estimates suggest that between 20 to 80 percent of people who contracted SARS-CoV-2 develop long COVID-19 symptoms, including fatigue, headaches, chest pain, breathing problems, and brain fog. But because the condition varies so much by person, some researchers suspect long COVID-19 may be even more common than current data suggests. Because long COVID-19 can occur after milder cases, some people suspect breakthrough cases in vaccinated people could lead to long-haul symptoms, too. There are many unknowns to long COVID-19, and our ability to track and treat the condition is limited by our understanding of it.