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One of the most frightening aspects of COVID-19 now seems to be the potential that symptoms could linger after an infection. What is my risk of having long COVID-19 if I become infected? And does being vaccinated change that?
Over the past year, a flurry of research has been published about long COVID-19. Dozens of these studies try to estimate the risk of having lingering symptoms months after a coronavirus infection.
But when you look closely at the data, a huge inconsistency emerges: The estimates of the prevalence of long COVID-19 range wildly, from less than 5% to nearly 60% of total COVID-19 cases. So what’s going on?
“It can be really confusing, even to scientists,” says Christina Pagel, who directs the Clinical Operational Research Unit at University College London.
One of the major problems is with this term “long COVID-19.” What scientists, doctors and the media have been calling “long COVID-19” isn’t just one disease or disorder. “It’s looking like what has been grouped together as ‘long COVID’ is actually two or three different groups of disorders,” Pagel says.
Each one of those disorders may have a particular set of symptoms and causes. Some affect populations differently than others do or linger for a different period of time.
Severe illness puts you at high risk of long COVID-19
Many of the early studies focused primarily on people who have been hospitalized with COVID-19. “Obviously, these people will have more severe illnesses,” says geriatrician Claire Steves at King’s College London. Some people spend time in the intensive care unit or on a ventilator.
With this severe illness comes a high risk of organ damage, either because of the virus itself or the body’s response to fight it. “Some people may have respiratory scarring and a kind of fibrosis that comes from having had inflammation in the lungs,” she says.
Some people have inflammation in their heart muscle, called myocarditis. Some have inflammation in their blood vessels or brain. “In some individuals, there’s definite evidence of changes in the areas of the brain that are sensitive to smell,” Steves says.
This tissue damage and inflammation can cause a whole host of lingering symptoms, including a fast heart rate, severe fatigue, breathing problems and cognitive problems.
And organ damage can take a long time to heal, no matter the cause of it. In fact, whenever a person is critically ill in the hospital, symptoms can linger, says primary care doctor and bioethicist Zackary Berger of Johns Hopkins University.
“It’s well known that people take a long time to recover after a critical illness,” Berger says. “So I think it’s not surprising that people who end up in the ICU would take longer to recover.”
Studies have found that for people hospitalized with COVID-19, the risk of lingering symptoms six months after the disease is quite high, around 50%, Steves says.
Mild or moderate illness can cut the risk considerably
Many news reports have suggested that the risk of getting long COVID-19 after a mild or moderate infection appears similar to the risk after a severe case. Indeed, some studies have found that up to 60% of people report one or more lingering symptoms six months…