FAQ: How Long COVID Is Defined, Diagnosed, and Managed in 2026

Long COVID remains clinically complex, with definitions that vary across health organizations and research studies. That variability affects who gets diagnosed, how patients are treated, and how outcomes are measured. Experts say clearer standards are critical to improving care and equity.

This FAQ examines how long COVID is clinically defined and what those definitions mean for diagnosis and care.

What is long COVID, and how is it clinically defined?

Long COVID can be defined as residual symptoms from the SARS-CoV-2 virus, according to the CDC.¹ However, recent studies vary in clinical definition, creating discrepancies in patient diagnosis and care strategies.² In comparison, the National Academy of Sciences, Engineering, and Medicine characterizes long COVID as prolonged COVID-19 or respiratory-related symptoms.

Despite variance in definitions from different health organizations, there are a few common symptoms that appear consistent across most definitions. These symptoms include:

• Feeling more tired than usual
• Pain or tightness in your chest
• Diarrhea (> 3 loose or looser than normal stools in 24 hours)
• Decreased smell or change in smell
• Fatigue, tiredness, or exhaustion

“We were comparing [definitions] across the ones that exist to sort of see how they stack up, and I think, really importantly, what the implications are for our ability to actually capture people who believe that they have long COVID,” Lauren Wisk, PhD, associate professor in the Division of General Internal Medicine and Health Services Research at the University of California, Los Angeles, said in an interview with The American Journal of Managed Care^®.²

Another differentiating factor between respiratory-related illnesses and long COVID is the number of symptoms present. Patients who may have long COVID presented with a higher count of overall symptoms when compared with those with other conditions.³

Who is most at risk for long COVID?

Anyone infected with SARS-CoV-2 can develop long COVID, according to the World Health Organization (WHO). However, some individuals may be at higher risk of developing it. These include women, older adults, smokers, and patients with overweight or obesity, or who have pre-existing chronic health conditions.⁴

“This is a long-standing and pervasive problem in the US health care system, and there are ongoing efforts to study, measure, and rectify these issues,” Wisk said. “But absent a universal payer system, where cost is not a primary barrier to access, such equity concerns will persist.”

Seeking health care immediately, should any symptoms arise, especially for high-risk patients, is a good preventative strategy, Kevin Ma, PhD, Epidemic Intelligence Service Officer in CDC's Coronavirus and Other Respiratory Viruses Division, said in a written Q&A with AJMC.

“The decision to vaccinate is a personal one,” he said. “People should consult with their health care provider to understand their options to get a vaccine and should be informed about the potential risks and benefits associated with vaccines.”

How is long COVID diagnosed and treated?

Long COVID is an exclusion condition, meaning there is no singular test or biomarker to confirm a long COVID diagnosis. The CDC recommends an SARS-CoV-2 test to help assess for current or previous infection.¹ Similarly, there is no singular treatment or cure for long COVID, but there are treatments and strategies that can help mitigate symptoms.

Long COVID was also added to the International Classification of Diseases as “Post COVID-19 Condition, unspecified.”¹ But the lack of a standard definition can present challenges when diagnosing patients, such as overdiagnosis and underdiagnosis.

“One of the other things that we have to worry about is both in terms of missing people who have long COVID but don't maybe meet the standard definition that was being used, but then also overdiagnosis,” Wisk said. “Including people thinking that they meet the definition, but then they don't actually have long COVID.”²

Can vaccinations reduce the risk of long COVID?

Numerous studies have associated COVID-19 vaccination with a reduced risk of long COVID and variants of SARS-CoV-2.⁵ COVID-19 is still a public health concern, as experts estimated between 380,000 and 540,000 patients were hospitalized between 2024 and 2025 due to the virus. And between 44,000 and 63,000 deaths occurred during that same period.

Recent data suggest the uptick in COVID-19 cases may be due to new variants of the virus shifting from XBB to JN.1 lineage. But a recent study, published in JAMA Network Open, found that in immunocompetent adults, the overall effectiveness of the 2024-2025 COVID-19 vaccines against hospitalization was 40%. The overall vaccine effectiveness also increased from 34% within the first 7 to 89 days after vaccination to 52% after the first 90 to 179 days.⁵

“Even vaccines with moderate effectiveness can reduce the risk of hospitalizations and deaths from COVID-19, especially in certain high-risk populations,” Ma said.

Additionally, in adolescents aged 12 to 17, COVID-19 vaccinations preceding the first infection reduced the risk of long COVID by 36%.⁵

How does long COVID affect long-term health and work?

Multiple health care experts and organizations have reported that COVID-19–related and long COVID symptoms have impacted patients’ performance and return to work after infection. In 2024, almost 14% of 3500 patients with long COVID did not return to work after getting sick.⁶

More recent studies have also shown that during the COVID-19 pandemic, there was an increase in work absences due to childcare, illness, or other personal reasons. Additionally, workers who experienced COVID-19-related absences for 7 days or longer were more likely to leave the workforce by 7 percentage points.

Prior research also noted a significant uptick in mean health-related monthly absences when comparing pre- vs post-pandemic periods, suggesting that the effects of SARS-CoV-2 have extended beyond acute infection and into longer-term workforce patterns.⁷

Taken together, these data indicate that long COVID is not only a clinical condition but also an economic and occupational health issue. Persistent symptoms such as fatigue, cognitive dysfunction (“brain fog”), dyspnea, and dysautonomia can limit full-time work capacity, reduce productivity, and increase reliance on medical leave or disability accommodations.²

“Health care providers should be aware of how to appropriately recognize cases of long COVID and assist patients in completing required paperwork when appropriate,” Wisk said.

References:
1. Long COVID clinical guidance. Centers for Disease Control and Prevention. July 24, 2025. Accessed February 23, 2026. https://www.cdc.gov/long-covid/hcp/clinical-guidance

2. McCrear S. Variable long COVID definitions create hurdles in care, research. AJMC^®. August 12, 2025. Accessed February 23, 2026. https://www.ajmc.com/view/variable-long-covid-definitions-create-hurdles-in-care-research

3. McCrear S. 5 things to know about long COVID. AJMC. August 22, 2025. Accessed February 23, 2026. https://www.ajmc.com/view/5-things-to-know-about-long-covid

4. Post COVID-19 condition (long COVID). World Health Organization. February 26, 2025. Accessed February 23, 2026. https://www.who.int/news-room/fact-sheets/detail/post-covid-19-condition-(long-covid)

5. McCrear S. 2024-2025 COVID-19 vaccines provided moderate protection against JN.1 variants. AJMC. February 19, 2026. Accessed February 23, 2026. https://www.ajmc.com/view/2024-2025-covid-19-vaccines-provided-moderate-protection-against-jn-1-variants

6. Cheng K. Long COVID keeps people out of work and hurts the economy. Yale Medicine. December 23, 2024. Accessed February 23, 2026. https://www.yalemedicine.org/news/long-covid-keeps-people-out-of-work-and-hurts-the-economy

7. McCormick B. Ongoing COVID-19 circulation linked to increases in health-related work absences, workforce exits. AJMC. October 22, 2025. Accessed February 23, 2026. https://www.ajmc.com/view/ongoing-covid-19-circulation-linked-to-increases-in-health-related-work-absences-workforce-exits