Researchers identify key symptoms of long COVID in young children

A new study has examined the most common long COVID symptoms in young children, revealing that these symptoms present differently than in adults

Long COVID affects people of all ages, including children and infants. It is estimated that 65 million people in the world have long COVID, with more being diagnosed each day.

Researchers at Mass General Brigham and their colleagues, as part of the federally funded RECOVER initiative, examined the most common long COVID symptoms in young children, finding that infants and toddlers (younger than two years old) were more likely to experience trouble sleeping, fussiness, poor appetite, stuffy nose, and cough. Preschool-aged children (three to five years old) were more likely to experience a dry cough and daytime tiredness or low energy. Results are published in JAMA Pediatrics.    

“This study is important because it shows that long COVID symptoms in young children are different from those in older children and adults,” said co-first author Tanayott (Tony) Thaweethai, PhD, associate director of Biostatistics Research and Engagement at Massachusetts General Hospital (MGH), a founding member of the Mass General Brigham healthcare system. Thaweethai is also an assistant professor at Harvard Medical School. “Children with these symptoms often had worse overall health, lower quality of life, and delays in development.” 

How does long COVID impact young children?

In this study, Thaweethai and fellow RECOVER researchers focused on younger age groups, including infants and toddlers, as well as preschool-age children. The study included 472 infants and toddlers, as well as 539 preschool-aged children, some of which had previously had COVID and some who had not. The children were enrolled between March 2022 and July 2024 from over 30 U.S. healthcare and community settings.  

The team examined various caregiver-reported symptoms that persisted for at least 90 days after COVID infection in both age groups, 41 symptoms in the infant/toddler group and 75 symptoms among preschool-aged children. They then compared children who had not experienced long COVID to children who had the condition to understand which symptoms persisted.  Within children who had been previously infected, 40 of 278 infants/toddlers (14%) and 61 of 399 preschool-aged children (15%) were classified as likely having long COVID. 

“We found a distinguishable pattern for both age groups of young children, including symptoms that are different than what we see in older children and adults,” said co-senior author Andrea Foulkes, ScD, director of Biostatistics at MGH, professor in the Department of Medicine at Harvard Medical School, and professor in the Department of Biostatistics at the Harvard T.H. Chan School of Public Health. “The tools from this study can be used in future studies to better understand long COVID in young children and develop ways to care for them.” 

In the report, the authors stated that the identified symptoms were used for research purposes, not for clinical diagnosis and that caregivers should consult a child’s clinician if they are concerned about symptoms of long COVID. They also note that their study relies on survey data, which can be affected by recall bias and may be challenging to report accurately for children too young to verbalise their symptoms and where antibody confirmation of infection may be incomplete.

The impact of COVID differentiates depending on age

In previous research from the same team, they found that children and teenagers also experienced long COVID symptoms in almost every organ system, and most had multiple symptoms affecting more than one system.

The researchers designed an index to identify children and adolescents who are most likely to have long-term COVID, finding that common symptoms were similar, yet slightly different between the two age groups. 

“The symptom patterns we observed tell us we should study and evaluate long COVID differently depending on the child’s age,” said Andrea Foulkes, ScD, a Mass General Brigham biostatistician and co-senior author on the study. “The index used for this study is the first step toward a clinical tool that will help us diagnose, and eventually treat, long COVID in children and teenagers.”