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Sharing our progress toward recovery

Research Summaries

Discover what the latest science from the RECOVER Initiative means for our ability to understand, diagnose, prevent, and treat Long COVID.

This page contains descriptions of findings from RECOVER research studies. These descriptions use plain language and a format that is easy to understand.

If you want to learn more about the scientific discoveries described here, you can also browse and search the complete list of RECOVER Publications.

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Long COVID may occur in people recovering from a COVID-19 infection and often includes symptoms related to the heart and lungs, which together are called the cardiopulmonary system. These symptoms, which include fatigue, shortness of breath, chest pain, cough, and reduced ability to do physical activity, can cause significant disability. This paper explores current knowledge about what causes Long COVID and how it affects the heart and lungs, in both adults and children. The authors also discuss how participants in the Researching COVID to Enhance RECOVERY (RECOVER) Initiative will help answer questions about the impact of Long COVID on the cardiopulmonary system. Understanding these causes and effects may help researchers discover new therapies for Long COVID symptoms. 

Short Summary
EHR Adult

Hill, EL; Mehta, HB; Sharma, S; et. al., BMC Public Health

An electronic health record, or EHR, is a digital file that contains information about a person’s healthcare. In this study, researchers studied anonymous EHR data from the National COVID Cohort Collaborative (N3C), a group of medical systems located across the United States. They compared a group of 8,325 people who had a Long COVID diagnosis or received healthcare at a Long COVID clinic to a group of 41,625 people who did not have Long COVID. The researchers found key differences between these 2 groups. They also identified risk factors that could make someone more likely to develop Long COVID, including being middle-aged (40 to 69 years old), being female, and having certain chronic (long-term) health conditions before they got COVID. Examples of these chronic health conditions were obesity and lung disease. More research is needed to better understand why and how the risk factors found in this study make someone more likely to develop Long COVID.

Researchers wanted to see if patients who had difficulty breathing while sleeping (Obstructive Sleep Apnea; OSA) were at higher risk for developing Long COVID compared to people without OSA. By comparing the electronic health record (EHR) data of COVID positive patients, researchers looked at the risk of developing Long COVID in patients with and without a previous diagnosis of OSA.

Researchers found that adults with a previous diagnosis of OSA had an increased chance of developing Long COVID when compared to patients that did not have a previous diagnosis of OSA.

Long COVID patients, caregivers, and community members contribute to all parts of RECOVER, including scientific research. These chosen members of the community are known as RECOVER Representatives. This paper, written by a team of RECOVER Representatives and researchers, talks about why they chose to work together and how their partnership has improved the study. They summarize some of the impacts of Long COVID and highlight the roles that patient advocacy can play in research. They also discuss what progress has been made so far in studying Long COVID and what challenges lie ahead. The authors state that the result of Representatives working together with researchers on study design, ways to include patients, and sharing community concerns has set a new example for the design of future biomedical research studies.

To understand Long COVID, researchers must be able to figure out which patients have it. Our understanding of Long COVID is evolving and it has been difficult to know who had Long COVID, especially in children. We need a reliable method to identify who might have Long COVID using existing health data.  

The purpose of this study was to create and test a computer program, called an algorithm, to find out which children have Long COVID based on their electronic health records (EHRs). EHRs (digital medical charts that have health data like doctor visits, lab results, and other health history) are an important source of data for research studies on Long COVID. The algorithm looks at EHRs to find patterns in the diagnoses, prescribed medications, procedures, and lab tests children received after having COVID-19. These patterns can be described as a phenotype, or a set of measured or visible traits, that can tell us who had Long COVID.    

The algorithm correctly identified 67% of the patients who had a Long COVID diagnosis from the EHRs. Among the patients who the algorithm said had Long COVID, 91% had a Long COVID diagnosis. Overall, the algorithm was correct in identifying whether a patient had a Long COVID diagnosis 99% of the time. This means the phenotype can be used to recognize which children have Long COVID in EHR data for future studies, or to screen patients to participate in clinical trials. 

Research Summary
Observational Adult

Thaweethai, T; Jolley, SE; Karlson, EW; et. al.RECOVER Consortium, JAMA

RECOVER researchers used data from the RECOVER observational cohort study in adults ages 18 and over. They compared symptoms reported in surveys by participants who did and did not have COVID.  

Researchers found 37 symptoms that participants who had COVID reported more often after having COVID compared to participants who never had COVID. 12 of these symptoms could identify participants with Long COVID, including feeling tired and unwell after activity, feeling weak and tired (fatigue), and brain fog. A definition of Long COVID based on symptoms is important for future research, including to find treatments. 

Short Summary
EHR Adult

Pfaff, ER; Girvin, AT; Crosskey, M; et. al.N3C and RECOVER Consortia, Journal of American Medical Informatics Association

A quick way for scientists to identify patterns in a large set of data is by teaching computers to find those patterns for them. To do this, the scientist creates a set of instructions for a computer to follow, called an algorithm, to locate exactly what the scientist is looking for. When that algorithm is plugged into a software program, a computer can run the algorithm many times and learn from it. This process improves the algorithm and it becomes more accurate over time. This is called machine learning. Machine learning can be very helpful and accurate, but it is also challenging to share between researchers because each computer can learn things on its own that can be difficult to recreate. When a computer arrives at an answer that a scientist cannot recreate, it is known as a black-box algorithm.

In order for one research team to share their findings with another research team, they must be able to recreate the steps of the algorithm to “de-black-box" it. This was done by researchers from the National COVID Cohort Collaborative (N3C) as part of the National Institutes of Health (NIH) RECOVER Initiative. The N3C team first identified a phenotype (measured or visible traits) for patients who were at a higher risk of developing Long COVID by creating and training a machine learning-based algorithm. Then, with RECOVER’s support, the N3C researchers worked with researchers from another NIH study called All of Us. They were able to re-create the machine learning-based algorithm, leading to the same phenotype. This means that they were able to “de-black-box" their algorithm. This case can be used as a guide of best practices when sharing algorithm data between research teams. This way, algorithms can be used by many research teams to better understand Long COVID.

To find another way to know if children had COVID, researchers compared health records of 2 groups of children: children who only had a positive antibody test and children who had a positive PCR test. A positive antibody test means a child had COVID in the past, had the COVID vaccine, or both. A positive PCR test means a child currently has COVID. Researchers used data from children’s hospitals in the National Pediatric Learning Health System (PEDSnet) network.

Antibody tests found 2,714 children who had COVID and didn’t have a positive PCR test or  COVID vaccine. If researchers used only PCR tests, they wouldn’t have known these children had COVID. Knowing if children had COVID is the first step to know their risk of Long COVID and if symptoms could be related to Long COVID.

Short Summary
Review Adult Pediatric

Mohandas, S; Jagannathan, P; Henrich, TJ; et. al.RECOVER Mechanistic Pathways Task Force, eLife

People who had COVID-19 may develop Long COVID, which is when someone may experience various health issues after having COVID. Many of these problems are due to a strong reaction to the SARS-CoV-2 virus by the immune system (the body’s defense system that fights infections). This reaction can happen a long time after the virus is no longer in the body.  

A healthy immune system can tell the difference between our body’s healthy cells and the harmful ones that can make us sick. However, an overactive immune system can make mistakes and cause harm because it may attack healthy organs and tissues. The immune system response to diseases like COVID is complex and different for each person.  

It is important to understand how the immune system works after having COVID for many different people, and this may require large, long-term studies. This paper reviews researchers’ current knowledge and the gaps in their understanding about the immune response after a COVID infection and how that may lead to both short-term and long-term problems.  

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