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8 trajectories for long COVID

Study captures variability of a condition that affects millions

Mass General Brigham Communications

November 17, 2025

3 min read

Millions of patients have developed long COVID, a chronic condition that involves a range of symptoms, including fatigue, brain fog, dizziness, and palpitations, that persist for at least three months after infection. In a new analysis of adult participants in an initiative called Researching COVID to Enhance Recovery, or RECOVER, Mass General Brigham researchers identified eight different trajectories that long COVID can take, depending on severity, duration, and whether symptoms improve or worsen. Their findings are published in Nature Communications.

“This study addresses an urgent need to define the differing long COVID trajectories,” said senior author Bruce Levy of Mass General Brigham’s Department of Medicine and Division of Pulmonary and Critical Care Medicine, and the Hersey Professor of the Theory and Practice of Physic at Harvard Medical School. “Our findings will help determine what resources are needed for clinical and public health support of individuals with long COVID and will also inform efforts to understand long COVID’s biological basis.”

10.3%

Of patients overall had long COVID symptoms 3 months after infection

To identify long COVID trajectories, the researchers followed 3,659 adult participants in the RECOVER initiative who first contracted SARS-CoV-2 during the Omicron variant era, after Dec. 1, 2021. The participants completed a comprehensive symptom questionnaire in three-month intervals up to 15 months post-infection to track changes over time. Then, the researchers identified patients with long COVID using the long COVID research index, a symptom-based tool that was previously developed by Mass General Brigham researchers.

Overall, 10.3 percent of patients had long COVID symptoms three months after infection, and 81 percent of these patients continued to experience persistent or intermittent symptoms a year later. Female patients and those who had been hospitalized with an acute infection were likelier to develop persistently severe long COVID symptoms.

The researchers identified eight different long COVID trajectories. Some of these trajectories included persistently severe symptoms, intermittently severe symptoms, gradually improving symptoms, gradually worsening symptoms, and mild symptoms that only appeared after 15 months.

“The variability we identified will enable future studies to evaluate risk factors and biomarkers that could explain why patients vary in time of recovery, and help identify potential therapeutic targets,” said first author Tanayott Thaweethai, an assistant professor of medicine at the Medical School and an assistant professor in the Department of Biostatistics at the Harvard T.H. Chan School of Public Health.

This research was funded by the National Institutes of Health.