Parents who thought their children were in the clear after recovering from COVID-19 may need to reconsider. A massive study tracking more than 460,000 young people across the United States has found that getting infected with COVID a second time doubles the risk of developing long COVID compared to a single infection.
The findings, published in The Lancet Infectious Diseases, challenge two widespread assumptions: that COVID in children is invariably mild, and that repeat infections carry less risk than the initial bout. Between January 2022 and October 2023, when the Omicron variant dominated, researchers from the National Institutes of Health’s RECOVER Initiative examined electronic health records from 40 pediatric hospitals. What they discovered was sobering.
After a first COVID infection, roughly 904 children per million developed long COVID within six months. After a second infection, that number jumped to 1,884 per million. The pattern held across demographics: vaccinated and unvaccinated kids, those with mild or severe initial infections, different age groups, races, and body weights all showed elevated risk after reinfection.
Heart Problems Top the List of Concerns
Among the conditions linked to long COVID in youth, myocarditis proved most alarming. This swelling of the heart muscle, which can weaken the organ and potentially prove fatal, tripled in risk after a second COVID infection compared to the first. Blood clots in children more than doubled. The researchers also documented increased risks for kidney damage, irregular heartbeats, persistent headaches, abdominal pain, and severe fatigue.
“The results of this study further support one of the strongest reasons I give patients, families and physicians about getting vaccinated: More vaccines should lead to fewer infections, which should lead to less long COVID.”
That’s according to Dr. Ravi Jhaveri, Head of Pediatric Infectious Diseases at Ann & Robert H. Lurie Children’s Hospital of Chicago and a study co-author. The statement cuts to the heart of a public health challenge: pediatric COVID vaccination rates remain stubbornly low, driven partly by perceptions that Omicron symptoms are mild, along with delayed vaccine availability for children under five and waning booster uptake among older kids.
The Hidden Toll Across Multiple Organ Systems
The study’s scope allowed researchers to track a wide range of health problems potentially tied to long COVID. Beyond heart and blood vessel issues, reinfected children faced heightened risks for respiratory symptoms, cognitive difficulties, mood disorders, and a condition called POTS (postural orthostatic tachycardia syndrome) that causes dizziness and rapid heartbeat when standing.
What makes this research particularly robust is its source material. Rather than relying on surveys or self-reported symptoms, as many previous pediatric long COVID studies have done, the team analyzed actual medical records with clinician-documented diagnoses. The sheer size of the cohort, nearly half a million children and adolescents, provided statistical power that smaller studies lacked.
“The level of coordination, data sharing, and analysis requires massive infrastructure and sustained support. Without this investment, we wouldn’t have had access to such a large and diverse pediatric population, nor the capacity to rigorously evaluate long COVID in a way that is applicable across many different levels of care.”
Senior author Dr. Yong Chen, a Professor of Biostatistics at the University of Pennsylvania’s Perelman School of Medicine, highlighted the collaborative effort required to pull off such ambitious research. The RECOVER Initiative, which funded the work, represents one of the largest coordinated research programs studying COVID’s long-term effects.
The study does have limitations. Home COVID tests, which became increasingly common during the study period, typically don’t make it into electronic health records. This means some infections, particularly mild or asymptomatic cases, may have been missed. The researchers also couldn’t fully account for timing issues: when exactly symptoms began, or how long they persisted.
Still, the patterns are clear enough to warrant concern. The research team plans to extend their tracking over longer periods, examine whether newer COVID variants change the risk profile, and explore specific prevention strategies. For now, the message remains straightforward: preventing infections in the first place, through vaccination and other measures, represents the most effective way to protect children from the cumulative burden of long COVID.
The 465,717 children in the study had a mean age of about 8 years, and half were male. The analysis controlled for dozens of factors including pre-existing health conditions, healthcare utilization patterns, and vaccination status. No matter how the researchers sliced the data, the elevated risk after reinfection persisted.
Whether COVID fatigue among the public will translate into renewed attention to pediatric vaccination remains uncertain. But the data suggest that assumptions about mild pediatric COVID may be premature, particularly as reinfections become increasingly common.
The Lancet Infectious Diseases: 10.1016/S1473-3099(25)00476-1
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