What if catching a seemingly common bug today meant a higher chance of organ damage years down the line for your child? It’s a sobering thought, but a major new study suggests this might be the reality for kids who’ve had COVID-19. Far from being a fleeting illness, new research indicates that even a mild bout of the virus could quietly increase a child’s risk of developing significant, long-term kidney problems. This isn’t just about bouncing back from a cough and fever; it’s about a potential lingering vulnerability to a vital organ.
This extensive research, published in the respected medical journal JAMA Network Open, shines a spotlight on an often-overlooked consequence of the pandemic. For a long time, the focus with children and COVID-19 has been on how most don’t get as sick as adults. While that remains true for the initial illness, a growing body of evidence, including this new study, points to “long COVID” affecting kids in unexpected ways. This particular research zeroes in on kidney health, sending a clear message to parents, doctors, and public health officials: the health journey after COVID-19 might be longer and more complex than we previously thought for our youngest.
Dr. Yong Chen, a senior author and professor at the University of Pennsylvania, emphasized the gravity of the findings: “While most public attention has focused on the acute phase of COVID-19, our findings reveal children face significant long-term health risks that clinicians need to monitor.” This statement reinforces the urgent need to adjust how we approach children’s health in a post-pandemic world.
Behind the Research: How Scientists Tracked Kidney Health
To uncover these insights, researchers embarked on an ambitious project as part of the National Institutes of Health’s (NIH) RECOVER Initiative. They brought together health records from 19 different medical centers across the U.S., covering patient visits over three years. By using de-identified electronic health records—meaning all personal information was removed—they could trace the health paths of a vast number of young patients without knowing their identities. This allowed them to compare the health of children who had COVID-19 against those who hadn’t.
The study looked back at existing health data, which is known as a retrospective study design. Their focus was specifically on children and teenagers under 21. They created two main groups: one with young people who had tested positive for the COVID-19 virus and another comparison group of those who consistently tested negative and had no record of infection.
When examining kidney health, the researchers looked for specific problems. One key area was new cases of chronic kidney disease (CKD). This is a long-term condition where the kidneys gradually lose their ability to filter waste from the blood. They specifically looked for signs of CKD at “stage 2 or higher,” which points to mild kidney damage, and “stage 3 or higher,” indicating more significant, even severe, damage affecting how well the kidneys work.
The team also tracked what they called “composite kidney events” for those who either had kidney problems before COVID-19 or who developed acute kidney injury (AKI) during their initial infection. AKI is a sudden, often temporary, decline in kidney function. These “composite events” included serious kidney issues like a big drop in kidney function (measured by a blood test called eGFR, or estimated glomerular filtration rate), needing dialysis, undergoing a kidney transplant, or reaching end-stage kidney disease. A lower eGFR number means the kidneys aren’t working as well.
To ensure fair comparisons, the researchers meticulously adjusted for many other factors that could influence kidney health. This included things like age, gender, race, ethnicity, obesity, and other ongoing health conditions. They used a sophisticated statistical technique called “propensity score stratification” to make sure the COVID-positive and negative groups were as similar as possible in these background characteristics. This helps bolster the confidence that any observed differences in kidney health could be linked to the COVID-19 infection itself.
The Alarming Truth: What the Data Revealed
The sheer size of this study lends significant weight to its findings. It included an astonishing 1,900,146 young patients. Nearly half a million (487,378) had a documented COVID-19 infection, while over 1.4 million (1,412,768) served as the comparison group. These children were almost equally split between boys and girls, with an average age of 8.2 years, and represented a diverse mix of racial and ethnic backgrounds from across the country.
The results are indeed cause for concern. For children and adolescents who had healthy kidneys before their COVID-19 infection, the study showed:
- Increased risk of mild kidney damage: Those who had COVID-19 faced a 17% higher chance of developing new-onset chronic kidney disease classified as stage 2 or higher. This indicates some degree of mild kidney damage, even if their kidneys were still generally functioning.
- Higher risk of more significant kidney damage: The risk climbed even higher, with a 35% increased chance of developing new-onset chronic kidney disease at stage 3 or higher. This level of damage means the kidneys are not working as effectively as they should. These heightened risks emerged within one month and continued for up to two years after the infection.
The study also shed light on children who were already vulnerable due to existing kidney issues or who developed kidney problems during their initial COVID-19 illness:
- For those with pre-existing chronic kidney disease: A COVID-19 infection was connected to a 15% increased risk of experiencing serious kidney problems (like needing dialysis or a major drop in kidney function) within about one to six months after infection. This elevated risk persisted for up to two years.
- For children who developed acute kidney injury (AKI) during their COVID-19 infection: These children faced significantly greater long-term kidney issues. They had a 29% increased risk of major kidney events between three and six months after infection, and this risk remained high for up to two years. Furthermore, there was a substantial 47% higher chance of a 50% or greater drop in kidney function in the period immediately following their acute illness, emphasizing the severe kidney damage experienced by this group.
It’s clear from these numbers: the chances of developing kidney problems after COVID-19 were consistently higher in children who had the virus, regardless of their previous kidney health status or whether they developed acute kidney complications during their initial illness.
Protecting Our Kids: A Call for Awareness
The message from this extensive study is unmistakable: COVID-19 is not just a respiratory illness, and its impact on children can extend far beyond the initial infection. The revealed link between the virus and increased risks of kidney damage, particularly in those with existing health challenges, highlights a crucial public health concern. While the acute symptoms of COVID-19 in children are often mild, these findings underscore that the effects on their bodies, especially their kidneys, can linger and potentially worsen over time. This research provides compelling evidence that long-term kidney issues are a genuine concern in young people who have had COVID-19. It reinforces the urgent need for medical professionals to consider the ongoing kidney health of children and adolescents after a COVID-19 infection, advocating for careful monitoring and proactive care to help protect their well-being for years to come.
Paper Summary
Methodology
This retrospective cohort study used de-identified electronic health records from 19 U.S. health institutions (NIH RECOVER Initiative) from March 2020 to May 2023, with up to two years of follow-up. It compared children and adolescents under 21 with confirmed SARS-CoV-2 infection to a control group without infection. Key outcomes were new-onset chronic kidney disease (CKD) and composite kidney events. Statistical analyses adjusted for numerous factors using propensity score stratification.
Results
Of 1,900,146 pediatric patients, COVID-19 positive individuals (487,378) had increased risks of post-acute kidney problems. For those without prior CKD, there was a 17% higher risk of new-onset CKD stage 2+ and a 35% higher risk of CKD stage 3+ (28 days to 2 years post-infection). For those with pre-existing CKD, COVID-19 was linked to a 15% increased risk of composite kidney events. Children with acute kidney injury (AKI) during acute COVID-19 faced 29-33% increased risks of composite kidney outcomes (3 months to 2 years post-infection) and a 47% increased risk of significant eGFR decline.
Limitations
The study’s retrospective nature means it shows associations, not direct causation. Reliance on electronic health records may limit data completeness and accuracy, particularly for kidney function measurements. While extensive adjustments were made for confounders, some unmeasured factors might still exist.
Funding and Disclosures
This research was part of the National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER) Initiative, primarily funded by the NIH (OT2HL161847-01). The article is open access and distributed under the CC-BY License.
Publication Information
The paper, titled “Kidney Function Following COVID-19 in Children and Adolescents,” was published in JAMA Network Open in 2025, Volume 8, Issue 4, with article number e254129. The Digital Object Identifier (DOI) is 10.1001/jamanetworkopen.2025.4129.