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Study shows that long COVID-19 lasts 18 months for most people

A new peer-reviewed study from Denmark showed that over half of people with severe cases of long COVID-19 failed to improve after 18 months. The study also showed that severe symptoms lasted for at least 18 months regardless of which variant of SARS-CoV-2, which causes COVID, infected the person.

Of course, the risk of long COVID-19 can be reduced by being fully up-to-date with vaccines that prevent the disease. If you don’t contract COVID-19 in the first place, you won’t get long COVID-19, and the vaccine reduces the risk of severe COVID-19.

Let’s take a look at what is “long COVID” and what this new study says.

Photo by Edward Jenner on

What is long COVID-19?

Long COVID, also known as chronic COVID, long-haul COVID, or long-term effects of COVID-19, is a form of COVID-19 infection that lingers for weeks, months, and, in many cases, years.

Most people get better within a few days or weeks after being infected, especially those who have been fully vaccinated. Unfortunately, a large proportion of individuals who get the disease first appear to recover, but the symptoms return for a long period (again, for years). They also develop new symptoms or health conditions within a few months of the original COVID-19 infection.

Long-COVID conditions do not affect everyone the same way. They can cause various types and combinations of symptoms in different people. The symptoms may affect other parts of the body, for example:

  • General symptoms, such as fatigue and fever
  • Respiratory symptoms, such as trouble breathing and cough
  • Heart symptoms, such as chest pain and palpitations
  • Neurologic symptoms such as trouble thinking and concentrating (“brain fog”), headaches, and sleep problems
  • Digestive symptoms such as diarrhea and stomach pain
  • Some people may have various symptoms similar to those of other conditions, such as chronic fatigue syndrome (CFS).

Although most individuals will improve over time, a significant number will continue to show these symptoms for years. Sometimes the symptoms are severe enough to result in disability.

Long COVID-19 study

In a paper published on 29 October 2023 in the International Journal of Infectious Diseases, the researchers analyzed data from 806 people in Denmark who were referred to the country’s specialized long COVID clinics because of severe symptoms.

Here are their key results:

  • The commonalities among people in the study who developed long COVID suggest that the condition’s cause is the same regardless of which variant led to the initial infection.
  • Those infected during the Omicron wave of the pandemic had symptoms that resulted in a lower quality of life.
  • People infected during the Delta and Omicron waves tended to be more physically exhausted.
  • Over half of the individuals who had long COVID-19 had symptoms that lasted at least 18 months.

The authors concluded:

We suggest the search for long COVID treatment options focus on these severely affected patients to develop future new treatments, which we believe will be effective across all SARS-CoV-2 variants


This research is troubling since we did not have firm evidence of how long COVID-19 might last for most individuals. This study shows that over half of people who get long COVID-19 have severe symptoms that last over 18 months. It is entirely possible that the condition could last several years or even become a permanent, chronic condition.

As a result of our need for more understanding of the disease, the US Department of Health and Human Services announced a $1.15 billion plan to better understand, treat, and prevent long COVID. In September 2023, the CDC found that 15% of US adults have had long COVID, and about 5% say they currently have the condition. That’s a huge number that has a large impact on the economy of the country.

There will be more studies published about this condition during the next few months and years. Stay tuned.


Michael Simpson

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