Since 2020, the disease known as long COVID-19 has become a widespread disability that affects the health and quality of life of millions of people around the world and costs economies billions of dollars due to reduced employee productivity and an overall decline in the workforce.
The intense scientific effort surrounding long COVID has resulted in more than 24,000 scientific publications, making it the most studied health problem in four years in human history.
Long COVID is a term that describes the constellation of long-term health effects caused by infection with the SARS-CoV-2 virus.
These symptoms range from persistent respiratory symptoms, such as shortness of breath, to debilitating fatigue or brain fog that limits people’s ability to work, to lifelong conditions such as heart failure and diabetes.
I am a physician scientist and have been deeply immersed in the study of long COVID since the early days of the pandemic.
I have testified before the US Senate as an expert on long COVID, published extensively on the topic, and was named one of Time’s 100 Most Influential People in Health in 2024 for my research in this area.
During the first half of 2024, a series of reports and scientific articles on long COVID have provided more clarity on this complex disease.
These include understanding how COVID-19 can still wreak havoc on many organs years after the initial viral infection, as well as emerging evidence of viral persistence and immune dysfunction lasting months or years after the initial infection.
How long does COVID affect the body?
A new study that my colleagues and I published in the New England Journal of Medicine on July 17, 2024 shows that the risk of long COVID has declined over the course of the pandemic.
In 2020, when the ancestral strain of SARS-CoV-2 was dominant and vaccines were not available, approximately 10.4% of adults with COVID-19 developed long COVID.
By early 2022, when the Omicron family of variants was predominant, that rate dropped to 7.7% among unvaccinated adults and 3.5% among vaccinated adults. In other words, unvaccinated people were more than twice as likely to develop long COVID.
Although researchers like me don’t yet have concrete numbers on the current rate in mid-2024 because of the time it takes for long COVID cases to be reflected in the data, the flow of new patients into long COVID clinics has been comparable to that of 2022.
We found that this decline was the result of two main factors: the availability of vaccines and changes in the characteristics of the virus, which made the virus less likely to cause severe acute infections and may have reduced its ability to persist in the human body long enough to cause chronic disease.
Despite the declining risk of developing long COVID, even a 3.5% risk remains substantial. New and repeat COVID-19 infections are resulting in millions of new cases of long COVID, adding to the already staggering number of people suffering from the disease.
Estimates for the first year of the pandemic suggest that at least 65 million people worldwide have had long COVID. Along with a group of other leading scientists, my team will soon publish updated estimates of the global burden of long COVID and its impact on the global economy through 2023.
Additionally, a major new report from the National Academies of Sciences Engineering and Medicine details all the health effects that make up long COVID. The report was commissioned by the Social Security Administration to understand the implications of long COVID on its disability benefits.
The study concludes that long COVID is a complex chronic disease that can lead to more than 200 health effects across many body systems. These include the onset or worsening of:
Long COVID can affect people of all ages, from children to older adults, regardless of race, ethnicity, or initial health status. It is important to note that more than 90% of people with long COVID have had mild COVID-19 infections.
The National Academies report also concluded that long COVID can lead to inability to return to work or school, poor quality of life, decreased ability to perform activities of daily living, and decreased physical and cognitive function for months to years after initial infection.
The report notes that many health effects of long COVID, such as post-exertional malaise and chronic fatigue, cognitive impairment, and autonomic dysfunction, are not currently captured in the Social Security Administration’s list of impairments but can significantly affect an individual’s ability to participate in work or school.
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A long road ahead
Additionally, health problems resulting from COVID-19 can last for years after the initial infection.
A large study published in early 2024 showed that even people who had a mild SARS-CoV-2 infection still had new health problems related to COVID-19 in the third year after initial infection.
These findings are similar to other research showing that the virus persists in various organ systems for months or even years after COVID-19 infection. Research also shows that immune responses to infection are still evident two to three years after mild infection.
Together, these studies could explain why a SARS-CoV-2 infection that occurred years ago could still cause new health problems long after the initial infection.
Significant progress is also being made in understanding the pathways by which long-term COVID wreaks havoc on the body.
Two preliminary studies from the United States and the Netherlands show that when researchers transfer autoantibodies (antibodies generated by a person’s immune system that are directed against their own tissues and organs) from people with long COVID to healthy mice, the animals begin to experience symptoms similar to those of long COVID, such as muscle weakness and poor balance.
These studies suggest that an abnormal immune response thought to be responsible for the generation of these autoantibodies may underlie long COVID and that eliminating these autoantibodies may hold promise as potential treatments.
A permanent threat
Despite overwhelming evidence of the multiple risks associated with COVID-19, many messages suggest that the disease no longer poses a threat to the population. Although there is no empirical evidence to support this claim, this misinformation has permeated public discourse.
The data, however, tell a different story.
COVID-19 infections continue to outnumber flu cases and cause more hospitalizations and deaths than the flu. COVID-19 also causes more serious long-term health problems. Trivializing COVID-19 as a harmless cold or likening it to the flu is not accurate.
Ziyad Al-Aly, Chief of Research and Development, VA St. Louis Health Care System. Clinical Epidemiologist, Washington University in St. Louis
This article is republished from The Conversation under a Creative Commons license. Read the original article.