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.
In this RECOVER study, researchers wanted to find out if natural language processing (NLP) could be used to identify Long COVID symptoms in children. NLP is a tool that can help find details in electronic health records (EHRs) beyond what is usually looked at in EHRs, such as diagnosis or billing codes (known as standard EHR data). Researchers used an NLP tool to look for 25 signs of Long COVID in children: 21 symptoms (like pain or extreme tiredness) and 4 types of daily life challenges (such as trouble with school). They compared children who had been diagnosed with Long COVID to those who had COVID-19 but did not develop Long COVID. The NLP tool analyzed more than 48,000 doctors’ notes within the EHRs of more than 10,000 children across 12 hospitals. Researchers found that the NLP tool identified almost all 25 symptoms much more often in the children who had Long COVID. The NLP tool also often identified patients’ symptoms that were not recognized when researchers only looked at standard EHR data. The study shows that using NLP to read EHR notes can help researchers better understand the symptoms and daily challenges that children with Long COVID experience when compared to looking only at codes and medication lists. This supports the idea that NLP should be used when doing scientific studies that need to identify children with Long COVID.
In this RECOVER study, researchers wanted to update a smart computer program, called a machine learning pipeline, to better identify people with Long COVID. In 2021, the first version of the program, called LCM 1, was created to identify people with or likely to have Long COVID. LCM 1 depended on people having a COVID-19 diagnosis date in their electronic health records (EHR). This meant LCM 1 could miss people who may have taken a COVID-19 test at home. LCM 1 also did not look at information about whether people got COVID-19 more than once. To improve the program and create a new version called LCM 2, researchers used more than 5 million EHRs from a large set of data called the National COVID Cohort Collaborative (N3C). They taught the program to look at a person’s health information over many years, not just starting from their first recorded COVID-19 diagnosis. Researchers found that LCM 2 was very accurate. They used it to estimate that about 1 in 10 people in the database who had COVID-19 went on to develop Long COVID. This study is important because it shows that older machine learning models, like LCM 1, can be updated to keep up with the way an illness is tracked and diagnosed over time. This can help other researchers improve their machine learning models to produce more accurate findings.
In this RECOVER study, researchers wanted to understand the connection between Long COVID and chronic kidney disease (CKD) in adults who had COVID-19. CKD is long-term, permanent damage to the kidneys. Researchers looked at the electronic health records (EHRs) of more than 2 million adults across 59 health systems in the US to see if people with CKD were more likely to develop Long COVID. The study found that, compared to people without CKD, those who had even mild cases of CKD were more likely to get Long COVID after COVID-19. Researchers also found that, compared to adults who did not get Long COVID, those who developed Long COVID and had healthy kidneys before getting COVID-19 were more likely to develop new CKD or have worsened kidney function within a year. These findings show how Long COVID and kidney disease can affect each other and highlight how important it is for doctors to monitor people’s kidney health after they get COVID-19.
In this RECOVER study, researchers wanted to find out if getting COVID-19 made young children more likely to get sick later. Some researchers believe that the immune system (the body’s defense system) won’t be able to fight off germs well after someone has had COVID-19. They also thought that children might be more likely to catch the cold-like virus that spread widely in 2022, called respiratory syncytial virus (RSV), or other lung infections after having COVID-19. To learn more, RECOVER researchers looked at the electronic health records (EHRs) of thousands of young children (those less than 5 years old) across 27 US health systems. They compared more than 133,000 young children who had COVID-19 to more than 37,000 young children who had the flu and more than 46,000 young children who had other respiratory infections. Researchers checked for RSV and other respiratory infections for 6 months in each group. They found the opposite of what was believed about the body’s immune system: young children who had COVID-19 were less likely to get RSV or other respiratory infections than young children in the other groups. This study is important because it suggests that getting COVID-19 may not make young children more likely to get RSV or other respiratory illnesses afterward.
This RECOVER study looked at how common Long COVID is in adults and children across the US. Researchers compared people who had COVID-19 to those who didn’t. They used data from 3 nationwide research networks that collect electronic health records (EHRs). Since there is no single definition for Long COVID yet, each network created its own working definition. These were based on earlier studies and symptoms that are commonly seen in people with Long COVID. Researchers then checked how many people had those symptoms between 1 and 6 months after having COVID-19. Findings were generally similar across the 3 networks. They found that about 4 out of every 100 children, and between 10 and 26 out of every 100 adults, developed Long COVID, depending on the definition of Long COVID used. The rates of Long COVID also changed over time, likely linked to new versions of the virus. Understanding how common Long COVID is and how this changes over time can help researchers learn who is most likely to get Long COVID.
In this RECOVER study, researchers wanted to find out whether children (ages 5–12) and teenagers (ages 12–20) who had COVID-19 were more likely to develop mental health conditions than those who never had COVID-19. Researchers studied the electronic health records (EHRs) of more than 1 million children and teenagers to see what mental health conditions they were diagnosed with after getting COVID-19. They found that children who had COVID-19 were more likely to be diagnosed with anxiety, obsessive-compulsive disorder (OCD), attention-deficit/hyperactivity disorder (ADHD), and autism. The researchers also found that teenagers who had COVID-19 had a higher risk of experiencing anxiety, depression, and thoughts of suicide. This study is important because it suggests that getting COVID-19 can increase the chance that young people will experience mental health conditions. Caregivers and doctors must recognize the risk of mental health conditions developing after COVID-19 to help young people get the treatment and support they need.
This RECOVER study looked at the link between COVID-19 severity (how mild or serious the illness was) and the chance of developing an autoimmune disease. COVID-19 severity ranged from no symptoms to being in the hospital and needing a breathing machine. The study also looked at which types of autoimmune diseases were most common after having COVID-19. Autoimmune diseases happen when the body’s immune system attacks its own healthy cells by mistake. Researchers used electronic health records (EHRs) from 3 nationwide research networks to study people who had COVID-19 between April 2020 and April 2021. They found that the most common autoimmune diseases in both children and adults after having COVID-19 were thyroid disease, a skin condition called psoriasis, and a gut problem called inflammatory bowel disease. In adults, inflammatory arthritis and Sjögren’s disease (an autoimmune disease that causes dry eyes, dry mouth, and joint pain) were also common. In children, Type 1 diabetes and autoimmune diseases involving blood were also found. The study's main finding was that people who were more severely ill from COVID-19 had a higher chance of developing an autoimmune disease than those who were less sick. This means that people with more severe illness likely had stronger immune reactions to COVID-19. This study shows a strong relationship between having severe COVID-19 and developing an autoimmune disease after getting COVID-19.
This RECOVER study looked at whether people with Human Immunodeficiency Virus (HIV) are more likely to get Long COVID after having COVID-19. HIV is a virus that attacks the body’s immune system. Researchers used electronic health records (EHRs) from 2 nationwide research networks of people ages 21 and older who had COVID-19. They divided them into 2 groups: people with HIV and people without HIV. Researchers used 2 methods to find people in the groups who might have Long COVID. One used a computer system that looked for Long COVID symptoms in medical records. The other looked for official diagnosis codes that doctors enter when they think someone has Long COVID. They found that people with HIV may have a slightly higher risk of being diagnosed with Long COVID when looking for Long COVID symptoms in medical records. However, they found that there was no clear link between having HIV and receiving the official diagnosis code for Long COVID. This suggests that Long COVID may be missed in people with long-term health problems like HIV.
This RECOVER study looked at whether children to young adults ages 21 and younger who had COVID-19 were more likely to have long-term kidney problems. Researchers reviewed the electronic health records (EHRs) of over 1.9 million children and young adults up to 20 years old. About 487,000 of them had COVID-19. They found that children and young adults who had COVID-19 were about 17% more likely to get a new kidney disease and about 35% more likely to get a more serious type of kidney disease. The risk of having worsening problems was high for children and young adults who already had kidney disease (about 15% more likely), or who had a kidney injury (about 29% more likely) when they were first sick with COVID-19. These findings are important because they suggest that doctors should closely monitor the kidney health of young patients after having COVID-19.
