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One of the most frightening aspects of COVID-19 now appears to be the potential for symptoms to persist after infection. What is my risk of having long-term COVID-19 if I become infected? And does vaccination change that?
Over the past year, a deluge of research has been published on long-term COVID-19. Dozens of these studies try to estimate the risk of persistent symptoms months after being infected with the coronavirus.
But if you look closely at the data, a huge inconsistency emerges: Estimates of the prevalence of long-term COVID-19 vary wildly, from less than 5% to nearly 60% of total COVID-19 cases. So what’s going on?
“It can be very confusing, even for scientists,” said Christina Pagel, head of the Clinical Operational Research Unit at University College London.
One of the biggest problems is with this term ‘prolonged COVID-19’. What scientists, doctors and the media are calling “long COVID-19” is not just one disease or condition. “It seems that what is grouped as ‘long COVID’ is actually two or three different groups of conditions,” Pagel says.
Each of those conditions can have a particular set of symptoms and causes. Some affect populations differently than others or stick around for a different period of time.
Severe illness poses a high risk of long-term COVID-19
Many of the early studies focused primarily on people hospitalized with COVID-19. “Obviously these people are going to have more serious illnesses,” says geriatrician Claire Steves of King’s College London. Some people spend time in intensive care or on a ventilator.
In this serious disease, there is a high risk of organ damage, either from the virus itself or the body’s response to fight it. “Some people may have scarring in the airways and a type of fibrosis that comes from inflammation in the lungs,” she says.
Some people have an inflammation in their heart muscle called myocarditis. Some have inflammation in their blood vessels or brain. “In some individuals, there is clear evidence of changes in the areas of the brain that are sensitive to smell,” Steves says.
This tissue damage and inflammation can cause a range of ongoing symptoms, including a rapid heartbeat, severe fatigue, breathing difficulties and cognitive problems.
And organ damage can take a long time to heal, regardless of the cause. In fact, when a person is seriously ill in the hospital, symptoms can persist, says primary care physician and bioethicist Zackary Berger of Johns Hopkins University.
“People are known to take a long time to recover from critical illness,” Berger says. “So I think it’s not surprising that people who end up in ICU take longer to recover.”
Studies have shown that for people hospitalized with COVID-19, the risk of lingering symptoms six months after the illness is quite high, about 50%, Steves says.
Mild or moderate disease can significantly reduce risk
Many news reports have suggested that the risk of contracting COVID-19 for a long time after a mild or moderate infection is comparable to the risk after a severe case. Indeed, some studies have shown that up to 60% of people report one or more persistent symptoms six months after contracting the coronavirus, including fatigue, brain fog, difficulty breathing, chest pain, cough, joint and muscle pain, abdominal pain, headache and anxiety or depression.
But many of these studies lack the so-called control group. That is, they don’t take into account that these symptoms are common in people who haven’t had COVID-19 — or who’ve had other types of infections. In other words, scientists aren’t sure if these symptoms are specifically related to COVID-19 or are typical of recovery from many infectious diseases that no one has paid attention to.
“There’s a belief that you have an infectious disease, you get your treatment for it and you’re done with it. You go back to work and you’re fine,” Berger says. “But for a lot of people, being sick isn’t like that.”
Take, for example, pneumonia caused by bacteria. Antibiotics can end the infection. But then many people have symptoms weeks later. “Half of people have breathing problems a month after having pneumonia,” Berger says. “That’s a lot of people, right?”
The same goes for the flu. And a study published in September clearly demonstrates this idea. Researchers in England analyzed the electronic health records of nearly 400,000 people with a confirmed flu or COVID-19 diagnosis. Then they looked at who had persistent symptoms. Nearly 60% of people with COVID-19 had at least one symptom that lasted for six months, but nearly 40% of people with the flu also had at least one ongoing symptom similar to that of people with COVID-19.
“Many people have persistent symptoms after infectious diseases,” Berger says. “I think we need to realize that.”
So, another type of “long COVID” might be people who need more time to recover from an infection, be it the flu, pneumonia, or COVID-19. In other words, there may have been “long flu” or “long-term pneumonia” all along, but it just wasn’t appreciated.
COVID-19 is likely a new trigger for post-viral syndromes
There is mounting evidence that SARS-CoV-2, the coronavirus that causes the disease COVID-19, can sometimes cause various post-viral syndromes, or diseases known to occur after infection. These include chronic fatigue syndrome, also called ME/CFS, and a blood circulation disorder called postural orthostatic tachycardia syndrome (POTS).
For example, one study that included 130 patients hospitalized with COVID-19 found that 13% of them met criteria for ME/CFS six months after their diagnosis.
dr. Peter Rowe of Johns Hopkins University has evidence that mild illness can also cause this disease. “We have a small sample size, but in that [patients] in whom the function remains impaired [six months] after COVID-19 infection…all met criteria for ME/CFS,” he wrote in an email to NPR. “I’m referring here to the patients who have long-lasting symptoms after mild COVID infections, not the hospitalized group , or those with organ damage after more severe acute COVID-19.”
More than 2 million Americans will be affected
So after you factor in these other causes of the so-called “long COVID”, you may be left with a condition specific to the SARS-CoV-2 coronavirus. “There is no standard definition for this syndrome yet,” says epidemiologist Ira Longini of University of Florida infectious diseases. “It’s a collection of symptoms, including shortness of breath, brain fog, fatigue, but also a problem with a particular organ or tissue, such as the heart or brain.”
This condition could be related to the virus invading an organ or tissue and persisting there, or persistent inflammation left over from the body that is fighting off the virus, Longini says.
It’s not yet known exactly what percentage of people will have this set of symptoms months after COVID-19, but Steves of King’s College London says her analysis from the UK indicates the risk is much lower in people who were not hospitalized included.
She says the Office for National Statistics in the UK currently has the best estimate for the prevalence of these long-term COVID-19 symptoms in this population. That data includes self-reports of more than a million people diagnosed with COVID-19.
“Overall… those data show that the rate of long-term COVID, more than 12 weeks after infection, is just under 5% of people,” Steves says.
Given the sheer number of COVID-19 cases in the US (and around the world), even a 5% rate means more than 2 million Americans (and nearly 13 million people worldwide) will be affected by this particular cluster of COVID – 19 symptoms for at least several months (and more will struggle with other post-viral problems).
Fortunately, Steves says, the percentage of people with these persistent COVID-19 symptoms drops dramatically one year after infection. “There are definitely individuals who still have symptoms for over a year, even up to 18 months now,” she says. “But there’s a very small percentage of those individuals. Gradually, most people get better. I see that in my clinic.”
But because so many people have been affected, health professionals need to be on the lookout for signs of any type of long-term COVID-19 — and be open to them, says Dr. Paddy Ssentongo, an epidemiologist at Pennsylvania State University. “Doctors have to listen to the patient. They tell you what’s happening to them. They don’t make up symptoms. Patients know best what’s going on with their bodies.”
How to reduce your risk of long-term COVID-19
The best way to reduce your risk of any long-term COVID-19 is to reduce your risk of getting a severe case of COVID-19. And to do that, Steves says, vaccination is at the top of the list. She and her colleagues have found that two-dose vaccination cuts the risk of getting the COVID-specific cluster of symptoms after infection in half.
But the vaccine’s overall effect on your risk of long-term COVID-19 is much greater, says Longini of the University of Florida. “The vaccine reduces the chance of infection with disease by maybe 70%. So overall, the long-term COVID reduction among vaccinated people is over 80 or 90%.
“That just shows the power of the COVID-19 vaccines,” he adds. They protect not only against acute diseases, but also against the various types of chronic diseases associated with the SARS-CoV-2 coronavirus.