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Study: Kids with COVID more likely to develop blood clots

By David Olson Updated August 5, 2022

Children who test positive for COVID-19 are much more likely to develop blood clots and cardiac problems weeks after their infection, compared with kids who did not contract the virus, a newly released study found.

The study, published Thursday by the Centers for Disease Control and Prevention, also found significantly higher rates of kidney failure and diabetes in those infected with the virus.

“A lot of the things they’re reporting are things that we're seeing,” said Dr. Howard Balbi, chief of pediatric infectious diseases at Good Samaritan Hospital in West Islip.

Many of the kids who develop complications a few weeks after infection, including some who ended up in intensive care, initially had mild or no COVID-19 symptoms, he said.


  • Children who tested positive for the coronavirus were significantly more likely to develop blood clots, cardiac problems, kidney failure and diabetes than kids who did not, a newly released CDC study found.

  • Long Island doctors said the study backs up what they’ve been seeing in hospitals. Many of the children who later developed complications initially had only mild COVID-19 or no symptoms at all, one pediatrician said.

  • Even though children are less likely to get severe COVID-19 than adults, the study shows that a small number of kids will develop serious health conditions, doctors say.

Dr. Andrew Handel, a pediatric infectious disease specialist at Stony Brook Children’s Hospital, said the study’s results “confirm our suspicions.”

“We know that most children who get COVID do not have severe infections from it,” he said. “But a small portion of these children are going to go on to have permanent organ damage as a result of the infection.”

The study is the largest ever in the United States on “post-COVID-19” effects on children, defined as symptoms and conditions four or more weeks after infection. CDC researchers examined medical records of more than 3.1 million children and adolescents, from infants to 17-year-olds, a quarter of whom had tested positive for the coronavirus and the rest who had not. The children were followed for between 60 days and a year.

Kids who had COVID-19 were twice as likely to have blood clots or lung-artery blockages caused by blood clots. They also were twice as likely to have cardiomyopathy, a disease of the heart muscle, or myocarditis, an inflammation of the heart muscle.

Last year, the CDC warned of rare cases of myocarditis among adolescent and young-adult males who received the Pfizer-BioNTech and Moderna vaccines. Some parents interviewed by Newsday and other media outlets said fear of myocarditis was a factor in not getting their children vaccinated.

But a CDC study released in April found that COVID-19 is far more likely than coronavirus vaccines to cause myocarditis, even among young males. The new study reiterates that COVID-19 is a greater myocarditis threat, Handel said.

In addition, he said, “What we’ve seen anecdotally in clinic [at Stony Brook] but also in research itself is that the myocarditis that kids get from the vaccine tends to be much, much, much less severe than when they experience it as a result of the infection itself. Generally, when kids get myocarditis after getting vaccinated, they can have some mild symptoms that usually just resolve on their own within a day or two. But myocarditis that you get with COVID infection itself can be devastating.”

COVID-19 causes inflammation, so it’s not surprising that the inflammation can continue for a longer period of time in some kids, said Dr. Mundeep Kainth, a pediatric infectious disease specialist at Cohen Children’s Medical Center in New Hyde Park.

“There is definitely already a known risk for that for anybody with COVID,” she said.

Children with COVID-19 also were about 1.3 times more likely to have kidney failure and roughly 1.2 times more likely to develop type 1 or type 2 diabetes or have issues with taste or smell, the study found.

The rate of malaise and fatigue among kids who had COVID-19 was only 1.05 times higher.

Studies have found that fatigue is the most common symptom of adults with “long COVID,” which the CDC defines as symptoms lasting at least three months after first contracting the virus.

Handel said he’s not surprised the rates of fatigue among kids aren’t higher.

“The symptoms that go along with what we're calling long COVID — fatigue, body aches, difficulty thinking and maybe some psychiatric symptoms — those are really much less common in children for reasons that we don't quite understand,” he said.

Kainth said the lower rates of fatigue also are probably because kids in general are more active than adults on average, and less likely to be fatigued.

Even so, Balbi said, multiple parents have told him that even though their kids who had gotten infected may not have severe post-COVID symptoms, “To quote the parent, ‘They're just not themselves four months later. ... They’re not back to normal. They’re not as active, they're not as interested in doing things.’ ”

Researchers cautioned that the study was not representative of the U.S. pediatric population. About 70% of the kids were enrolled in Medicaid managed care. In addition, the analysis was based on medical records — meaning the children in the study who did not contract the coronavirus “were seeking medical care,” Kainth said. “These were not completely healthy kids.”

If healthier children had been part of the study, there may have been an even larger gap between kids who had COVID-19 and those who had not, she said.

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