November 19, 2025, 7:02 pm | Read time: 4 minutes
A recent study shows that around ten percent of COVID-19 patients suffer from long COVID for months afterward. However, researchers have also identified eight different courses that long COVID can take.
U.S. Study with Over 3,500 COVID-19 Infected
Long COVID is a condition that can develop as a result of a COVID-19 infection. For months, affected individuals suffer from symptoms such as fatigue, concentration and memory problems (known as brain fog), dizziness, heart palpitations, and insomnia.1 According to a recent U.S. study with more than 3,500 participants, 10.3 percent of those previously infected with COVID-19 still showed long COVID symptoms three months after infection.2 Eighty-one percent of long COVID patients still suffered from it a year later. But the researchers discovered more: Apparently, there are eight different courses that long COVID can take.
How Researchers Studied Long COVID Courses
As part of the “Researching COVID to Enhance Recovery (RECOVER)” initiative, researchers from the U.S. hospital association “Mass General Brigham” studied the different courses of long COVID. They used criteria such as the severity, duration, and recovery process of symptoms.
For the study, 3,659 adults from the RECOVER initiative were recruited. All these study participants were first infected with the Omicron variant of the coronavirus (after December 1, 2021). Subsequently, participants had to complete a comprehensive symptom questionnaire three, six, nine, 12, and 15 months after infection. This allowed researchers to observe the course of symptoms over a long period.
Using the data, patients with long COVID were identified by employing the so-called “Long COVID Research Index.” This index translates the individuals’ existing complaints into a score. Based on this score, a probable and a possible illness can be distinguished.3
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What the Data Analysis Revealed
As mentioned above, around ten percent of those infected with COVID-19 developed a long COVID condition, which persisted in 80 percent of cases for more than a year. Here are the detailed numbers:
- In total, 195 patients (five percent) had persistently severe long COVID symptoms.
- 443 patients (12 percent) had non-resolving, occasionally severe symptoms.
- 526 patients (14 percent) no longer met the criteria for long COVID after three months, but had increasing symptoms after 15 months.
- After three months, 377 patients (10 percent) met the criteria for long COVID. Of these, 175 (46 percent) had persistent long COVID, 132 (35 percent) had moderate symptoms, and 70 (19 percent) seemed to be recovering.
Additionally, the data showed that female patients and those hospitalized with an acute COVID-19 infection were more likely to develop persistently severe long COVID symptoms.
Furthermore, researchers identified eight different long COVID courses. They classified them as follows:
- persistently severe symptoms
- occasionally severe symptoms
- gradually improving moderate symptoms
- gradually improving mild symptoms
- gradually worsening moderate symptoms
- mild symptoms that appeared only after 15 months
- consistently minimal to no symptoms
- consistently mild symptoms
The Results Can Help in Treating Long COVID
The researchers responsible hope the study will contribute to better treatment for affected patients. “Our findings will help determine what resources are needed for clinical and health policy support for people with long COVID, and they will also contribute to efforts to understand the biological underpinnings of long COVID,” said lead author Bruce Levy in a press release from the Mass General Brigham Department of Medicine.4
Nevertheless, further studies are needed to understand why some patients develop severe long COVID courses and others do not. “The differences we identified will enable future studies to assess risk factors and biomarkers that could explain why patients have different recovery times and help identify potential therapeutic targets,” commented the study’s first author, Dr. Tanayott Thaweethai, on the findings.
How those affected can be helped is already shown by earlier studies. Recently, FITBOOK reported on how strength training helps against long COVID symptoms.