March 21, 20205 — Vaccinated children are much less likely to develop “long COVID” than are unvaccinated children, according to a new study that researchers hope will convince parents to keep kids’ immunizations up to date.
Many parents don’t get their children vaccinated against COVID-19 because pediatric cases are generally mild. But the study of post-COVID condition (PCC), as scientists call long COVID, supports continued vigilance, researchers say.
The new study looked at children ages 5 to 17 in four states from July 2021 through May 2023. If they’d been vaccinated prior to infection, their chances of developing one or more PCC symptoms were reduced by 57%.
“Vaccines don’t always prevent infection, but if you are infected, the body has a defense system ready to go, so the infection doesn’t get worse,” said study co-author Sarang Kim Yoon, DO, associate professor of occupational and environmental health at the University of Utah Medical School.
While adults are more likely to get long COVID than are children, the risk of pediatric PCC is between 1% and 3% among those infected with COVID, the authors noted.
“It was a minority of the kids who developed long COVID, but the majority of the vaccinated kids did pretty well,” Yoon said. “So the recommendation from this study is to vaccinate kids.”
What the Research Showed
Of the 622 children who had at least one positive COVID test during the study period, 28 (5%) reported PCC symptoms and 594 (95%) didn’t report any during the follow-up period.
PCC is defined as a persistent illness lasting four or more weeks after the initial phase of infection. Symptoms included respiratory issues, fatigue, weakness, difficulty in exercising, change in energy level, mood changes, and sleep disturbance. In rare cases, PCC may cause serious symptoms such as acute pulmonary embolism, myocarditis, cardiomyopathy, kidney failure, and type 1 diabetes.
Of the children with PCC in the study, 57% had been vaccinated.
Vaccinated children had a 73% reduced likelihood of two or more PCC symptoms and a 72% reduced likelihood of respiratory PCC symptoms.
The authors noted that vaccination protection against PCC may be even stronger than the numbers suggest. This is because both the case and control groups had been infected at some point, and the estimates did not look at how many infections vaccination prevented in the first place.
Generally, between 10% and 30% of children hospitalized for COVID have severe illness, according to the CDC.
Of the 28 kids in the study with long COVID, 21 had more than one post-COVID symptom. “The most concerning symptom was respiratory issues, which 19 of them had,” she said. “In terms of impact on function, long COVID impacted their daily activities such as going to school and participating in sports.”
Respiratory symptoms include shortness of breath, difficulty breathing, runny nose, nasal congestion, and coughing, she said. Non-respiratory symptoms included fever, change in weight (up or down), rashes, and chest pain.
What It Means for Parents
A group of CDC researchers who participated in the study told WebMD that “while PCC after vaccination is still possible, vaccination both reduces the risk of any PCC and reduces the risk of having multi-symptom PCC.”
William Schaffner, MD, professor of preventive medicine and of infectious diseases at Vanderbilt University School of Medicine, called the new paper “a large and well-done study.”
“It reinforces data in the literature showing that vaccination reduces the risk of COVID symptoms developing in both adults and children,” he said. “That’s the best you can hope for in these respiratory virus vaccines.”
Yoon said a separate ongoing study on long COVID includes a pediatric section that will help clarify how long persistent symptoms might last.
The new study noted that most American children have had some exposure to COVID. But Schaffner, a member of the CDC’s Advisory Committee on Immunization Practices (ACIP), emphasized that they should still be vaccinated even if they have some immunity.
“That’s because the virus keeps mutating,” he said. “It changes over the course of the year — and just as we do with influenza vaccine, we update COVID vaccines to keep pace with the virus, so it updates your prevention. And for the most vulnerable children — who are at high risk of serious disease — the importance of keeping your immunity in tip-top shape is important.”
Only 12% of U.S. children have received COVID shots updated for 2024-2025, about half of the percentage for adults. “The impression of the average parent is that COVID has evolved and that now these Omicron variants out there are much less serious,” Schaffner said.
“Children have always been less seriously affected than have adults, but that difference has been emphasized more and more. So parents don’t seek the benefits of vaccination very much, and the concerns about rare side effects such as endocarditis loom high in their thinking,” Schaffner said.
