Researchers identify key symptoms of long COVID in young children

Long COVID—symptoms that linger long after the initial viral infection—can affect people of every age, including children. But the lasting symptoms in an infant, toddler, or pre-school-aged child may be different than symptoms in adults and older children.

A new study conducted by researchers at Mass General Brigham and their colleagues as part of the RECOVER initiative examined the most common long COVID symptoms in young children, finding that infants and toddlers (younger than 2 years old) were more likely to experience trouble sleeping, fussiness, poor appetite, stuffy nose, and cough. Preschool-aged children (3 to 5 years old) were more likely to have a dry cough and daytime tiredness/low energy.

The 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, Ph.D., associate director of Biostatistics Research and Engagement at Massachusetts General Hospital (MGH), a founding member of the Mass General Brigham health care system.

“Children with these symptoms often had worse overall health, lower quality of life, and delays in development.” Thaweethai is also an assistant professor at Harvard Medical School.

The new study is the latest publication from Researching COVID to Enhance Recovery (RECOVER) initiative, which seeks to explore the effects of long COVID across all ages.

This paper builds on a previously published study that examined long COVID symptoms in school-aged children (6 to 11 years old) and teenagers (12 to 17 years old).

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

Researchers looked at a variety of caregiver-reported symptoms lasting at least 90 days after COVID infection for both age groups—41 symptoms in the infant/toddler group and 75 symptoms among preschool-aged children. They compared children who had not been previously infected to those with a history of COVID to see which symptoms persisted.

Among 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.”

The authors note that the symptoms reported in the paper have been identified for research purposes, not for making a clinical diagnosis and that caregivers should talk to 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 difficult to report accurately for children too young to verbalize their symptoms and where antibody confirmation of infection may be incomplete.