When Lucas Denault was first infected with COVID in January 2021 at the age of 15, his symptoms were relatively mild. A high school athlete at the time, the Pennsylvania resident experienced a brief bout of cold-like symptoms, recovered, and resumed his life.

But 3 months later, he was infected a second time, and it hit him harder and lasted longer — his condition became long COVID. “The long COVID symptoms came around early April… I went from 100% to being bedridden in about 2-3 weeks,” Denault recalled. For nearly 2 years, he was plagued by debilitating dizziness, chronic fatigue, and cognitive dysfunction.

Now, a landmark new study reveals that Denault’s experience is more common than previously believed. Children and teens who get COVID a second time face twice the risk for developing long COVID, researchers concluded.

The study, the largest of its kind using health records from nearly half a million American children, also found that a reinfection significantly raises the odds of a worse outcome.

A reinfection more than triples the risk for myocarditis, a dangerous inflammation of the heart muscle, and more than doubles the risk of life-threatening blood clots, the researchers reported. They also documented a nearly twofold increase in the risk for acute kidney injury and a rise in debilitating symptoms like altered taste and smell, as well as cognitive impairment.

The study paints a picture that is becoming increasingly familiar to specialists on the front lines.

“We see kids that have multiple infections with COVID come to our clinic, and oftentimes it was not the first infection that triggered their long COVID symptoms,” said Alexandra B. Yonts, MD, director of the pediatric Post-COVID Program at Children’s National in Washington, DC. 

“Often it was not even the second or the third or the fourth. We’ve had some kids that had it five, six, seven times.”

When a Clear Scan Isn’t Enough

Lucas’s journey illustrates the profound challenge pediatricians face. Early on, doctors suspected he had myocarditis, but when tests showed his heart was fine, they didn’t immediately think to consider long COVID.

“If everything [with my heart] looks good but there are still [physical and mental] struggles, what’s the next step?” Denault said. “After [doctors] said my heart was fine, there was no next step. They said, ‘Well, there’s no problem with your heart, so there is no problem to address.’” It was only when his symptoms stretched on for more than a few months, the CDC’s threshold for long COVID, that his doctors concluded that he had the condition. The problem, Yonts said, is that after a second SARS-CoV-2 infection, the danger escalates. 

“There’s additive risk beyond two infections,” she noted. “With each subsequent infection, there’s increased risk of developing [long COVID] if you don’t have it, but also worsening symptoms if you already do.”

Another problem: There is no standard diagnosis for long COVID beyond the length of time symptoms last.

A survey of pediatric healthcare providers revealed marked variability in their threshold for considering long COVID and their diagnostic approaches. Some doctors recognize it immediately; others don’t. Parents may experience significant frustration when seeking care for their child, as diagnosis is often complicated by a lack of standardized guidelines.

What Symptoms Should Raise Red Flags?

For pediatricians, recognizing long COVID requires vigilance, especially when families don’t connect lingering symptoms to past infections, Yonts said.

“This is real, and this is a biologic, new-onset chronic illness,” said Yonts.

According to Laura Malone, MD, PhD, the doctor who treated Lucas for long COVID, the most common symptoms pediatricians should watch for are profound fatigue and post-exertional malaise, also known as post-exertional symptom exacerbation. This is a debilitating and hallmark symptom of long COVID, where even minor physical or mental effort results in a severe crash, often delayed by hours or days, that can leave a patient bedridden.

For Denault, this meant a simple stress test left him so dizzy he was throwing up and couldn’t walk out of the doctor’s office on his own, said Malone, director of the Pediatric Post-COVID-19 Rehabilitation Clinic at the Kennedy Krieger Institute, Baltimore. 

“I could get up and run on the treadmill for 10 minutes, but then I couldn’t walk out of the doctor’s office because I was so dizzy and throwing up,” he recalled.

A Lifeline of Specialized Care

An estimated 5.8 million American children are potentially affected by long COVID, but fewer than 20 pediatric specialty clinics in the country offer specialized care. The Denaults were fortunate; a cancellation got him into Kennedy Krieger after a few months, avoiding what was a year-long waitlist.

It was there, under Malone’s care, that Denault finally received a diagnosis — postural orthostatic tachycardia syndrome, a condition associated with long COVID — and a treatment plan that changed everything. 

A key part of that plan was the medication midodrine, used to manage hypotension, which Denault called his “miracle drug.”

“It got me kind of off the couch and into the classroom, which was really awesome,” he said. “It definitely gave me a boost.”

The second part of his recovery was a meticulous physical rehabilitation regimen, monitored by Malone. The goal was to find a delicate balance: doing enough exercise to challenge his body without pushing it into a relapse.

This painstaking process, which also included a rigid sleep schedule and structured daily routines, eventually paid off. Nearly 2 years after contracting long COVID, Denault, who once needed a wheelchair for college tours, stepped onto the basketball court for his senior season.

“He went out there, and we thought he was ‘the man,’” his mother, Karin, recalled. “The crowd went wild.”

Breaking the Cycle: Education and Prevention

Programs like Kennedy Krieger’s ECHO have trained nearly 100 professionals, significantly increasing their ability to diagnose and manage long COVID.

Participants reported a 21% increase in their ability to diagnose and manage the condition. The program aims to extend reach beyond major medical centers and into local communities where specialized care is needed most.

While education is critical, prevention remains the strongest tool, experts said. A RECOVER study of over one million children found that vaccination reduced long COVID risk by 35% overall and 50% in adolescents, though effectiveness waned over time — so boosters remain of paramount importance.

“Both JAMA and Pediatrics publications showed decreased risk of long COVID for children that had been vaccinated,” Malone said.

Yonts advocates vaccination even for children already experiencing symptoms. 

“Revaccination, keeping up to date on boosters, and giving your body that leg up on the immune response — in my mind, is the better way to go, even if it means a couple of days of transient symptom worsening,” she said.

The American Academy of Pediatrics in August 2025 recommended COVID vaccination for all children aged 6-23 months and high-risk children aged 2-8 years.

Today, Denault — now 20 years old — is studying aerospace engineering at Princeton University, Princeton, New Jersey. His harrowing 2-year battle underscores the profound danger of long COVID, and the new data on reinfection serves as a critical alert: every subsequent infection is a gamble with a child’s long-term health, Malone and Yonts said.

Even in recovery, the illness has left a lasting imprint. He has become, in his own words, “a professional at kind of listening to my body and understanding what to do and when.”

That vigilance is most necessary during stressful periods like taking university exams. 

“Everyone feels kind of a brain fog [studying for exams],” he explained, “but it’s definitely a little bit more extreme and exaggerated for me.”