What exactly is Long COVID? New UCLA research shows the answer depends on whom you ask
Lack of a standard definition leads to widely varying estimates, complicating care and research
What is Long COVID? Despite hundreds of published studies and millions affected worldwide, the medical field still lacks a clear answer.
New research from UCLA finds that the definition of Long COVID varies so widely across published studies that the percentage of people identified as having the condition can differ dramatically, making it harder to treat patients and advance research.
The study, published August 12 in JAMA Network Open, highlights just how much the lack of a standard definition is clouding our understanding of Long COVID.
“The findings highlight the need for a standard definition for Long COVID,” said study lead Lauren Wisk, an assistant professor of medicine in the division of general internal medicine and health services research at the David Geffen School of Medicine at UCLA. “Up to one third of the variation in the published studies may stem from the fact that they use different definitions for Long COVID.”
Using data from 4,700 U.S. patients in the CDC-funded INSPIRE cohort, UCLA researchers applied five published Long COVID definitions from studies conducted in the US, U.K., Netherlands, Sweden, and Puerto Rico. The result? Depending on which definition was used, the estimated prevalence of Long COVID ranged from 15% to 42% - all in the same group of patients.
The five definitions assessed in the study differed by symptom duration (4 weeks to 6 months) and number of symptoms considered (9 to 44), resulting in reported prevalence of Long COVID that ranged from 2.6% to 61.9% in the original studies. When these different published definitions were applied to the INSPIRE cohort, these differences also created significant variation in who was labeled as having Long COVID.
Researchers also found that published definitions had only moderate sensitivity –the ability to correctly identify those with the disease— compared to participants’ own self-reported experience of Long COVID. While specificity of these definitions was better, none of the definitions reached an ideal level to be considered the optimal identification test.
“If every study on Long COVID uses a different definition for identifying who has it, the scientific conclusions become harder to compare across studies and may lead to delays in our understanding of it,” Wisk said. “In the absence of an objective measure, like a blood test, or a uniform standard for measuring Long COVID, researchers and clinicians will need to decide which definition is best suited for their scientific question and be more transparent about the potential limitations of using a more vs less restrictive definition.”
These differences may lead researchers and physicians to miss some legitimate Long COVID cases and to label some patients as having Long COVID when they don’t, said Dr. Joann Elmore, professor of medicine in the division of general internal medicine and health services research at the David Geffen School of Medicine at UCLA and the study’s senior author.
“Without a clinically usable and standardized research definition of Long COVID, it’s like every study is using a different measuring stick,” she said. “That makes it hard to compare results, develop treatments, or track progress. Without a shared definition, we risk mislabeling patients and misguiding care. This is more than an academic debate- it affects real people.”
Study limitations include potential recall bias among participants; participant demographics that may have influenced prevalence were unexamined, and results may have differed had the researchers included more than the five published studies in their analysis.
Study co-authors are Michelle L’Hommedieu and Kate Diaz Roldan of UCLA, and others from the INSPIRE Group.
INSPIRE was funded by the National Center of Immunization and Respiratory Diseases (75D30120C08008) in the Centers for Disease Control and Prevention.
Journal
JAMA Network Open
Method of Research
Literature review
Subject of Research
People
Article Title
Variability in Long COVID Definitions and Validation of Published Prevalence Rates
Article Publication Date
12-Aug-2025
Work impairment and financial outcomes among adults with vs without long COVID
JAMA Network
About The Study:
In this prospective cohort study of adults with SARS-CoV-2 infection, participants with current self-reported long COVID (defined as developing new, persistent symptoms lasting 3 months or longer after SARS-CoV-2 infection) reported worse work impairment, missed work, and financial distress compared with those who never had long COVID, while vaccination was associated with improved work outcomes and less financial distress even among individuals with long COVID. These data underscore the need for post-pandemic assistance programs, as well as vaccination to decrease societal harms.
Corresponding Author: To contact the corresponding author, Michael Gottlieb, MD, email MichaelGottliebMD@Gmail.com.
To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/
(doi:10.1001/jamanetworkopen.2025.26310)
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
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About JAMA Network Open: JAMA Network Open is an online-only open access general medical journal from the JAMA Network. On weekdays, the journal publishes peer-reviewed clinical research and commentary in more than 40 medical and health subject areas. Every article is free online from the day of publication.
Journal
JAMA Network Open
U.S. Study: Long COVID remains a substantial financial and medical burden
But being vaccinated lessened financial and employment impact
Rush University Medical Center
Chicago, Ill Aug 12, 2025) While the economic impact of the COVID-19 pandemic continues to be widely studied and debated, the financial toll of the COVID-19 pandemic for individual patients is less understood. To address this gap, Rush University Medical Center analyzed self-reported data from more than 3,600 participants in the INSPIRE (Innovative Support for Patients with SARS-CoV-2 Infections Registry) to assess return-to-work, work productivity, and financial toxicity.
The INSPIRE study found that individuals with long COVID-19 experienced worse financial and employment outcomes – lasting up to three years after their initial infection. Notably, vaccination against COVID-19 was associated with strikingly improved work and financial outcomes. The study, “Work Impairment and Financial Impact among Adults With vs. Without Long COVID”, was published Aug. 12 in JAMA Network Open.
INSPIRE is a CDC-funded multi-center collaboration including eight academic medical centers seeking to better understand the long-term effects of COVID-19.
“While much of the focus in Long COVID research has been on the medical impact, we must also consider the sustained financial burden faced by those whose symptoms persist,” said lead author Michael Gottlieb, MD, an emergency medicine physician and vice chair of research at Rush University Medical Center Gottlieb and co-authors suggest that better understanding of the economic challenges millions of Americans face can lead to better workplace policies, disability support systems, and health care strategies.
Of the more than 777 million reported cases of COVID-19 worldwide, data compiled by the Agency for Healthcare Research and Quality suggest that approximately 13% of patients experience persistent symptoms lasting three months or longer, a condition which is commonly referred to as long COVID.
Gottlieb and colleagues working on the INSPIRE research already have contributed valuable scientific data about the medical nature of Long COVID, such as identifying that it is not a single condition but rather four distinct symptom patterns, called phenotypes, which can help guide treatments. INSPIRE’s unique, long-standing self-reported survey structure also helps researchers better understand and measure the financial burdens associated with the illness and, importantly, the beneficial effect of prior vaccination. Researchers used survey responses to track the degree of missed work and work impairment and a tool long used by cancer researchers to calculate “financial toxicity,” which estimates the negative consequences experienced by patients due to the cost of medical care.
Three years of study data revealed that those with Long COVID continue to experience significantly higher odds of missing more work per week than those who did not have Long COVID. Nearly half of participants currently experiencing Long COVID had not returned to full-time work within three years of their initial infection.
Financial toxicity scores also showed that those with Long COVID had more than three-times higher odds of moderate-to-high financial toxicity compared to those whose Long COVID symptoms had resolved, and more than five-times higher odds compared to those who never experienced Long COVID.
Authors noted that this financial strain could be caused by medical expenses, job loss, reduced work-hours due to limited work capacity, or lower work productivity resulting in reduced bonuses or raises.
Gottlieb emphasized that vaccination status had a clear impact on rates of work impairment and financial toxicity scores with markedly better outcomes in the vaccinated patients compared with the unvaccinated patients. This is consistent with other recent research from their team which also identified improved physical and mental health outcomes among those who were vaccinated against COVID.
“Throughout all or our research, whether someone was vaccinated was shown to be strongly associated with more symptom reduction and measurably better quality of life. The COVID-19 vaccine kept us healthier — both physically and financially.”
Journal
JAMA Network Open
Method of Research
Randomized controlled/clinical trial
Subject of Research
People
Article Title
“Work Impairment and Financial Impact among Adults With vs. Without Long COVID”
Article Publication Date
12-Aug-2025
COI Statement
None from lead author. But co-authors report: Dr Gentile reported grants from the National Center for Complementary and Integrative Health (NCCIH), National Institute on Aging, and Agency for Healthcare Research and Quality (AHRQ) outside the submitted work. Dr Geyer reported grants from AHRQ and NCCIH outside the submitted work. Dr Elmore reported serving as Editor-in-Chief of Primary Care for UpToDate. Dr Wisk reported grants from National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and National Institute of Mental Health (NIMH) outside the submitted work. Dr Montoy reported grants from Substance Abuse and Mental Health Services Administration (SAMHSA), the US Food and Drug Administration (FDA), and grants from National Institute of Neurological Disorders and Stroke (NIHDS) during the conduct of the study. Dr Rising reported grants from the Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH) outside the submitted work. Dr Venkatesh reported grants from SAEM Foundation outside the submitted work. No other disclosures were reported.
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