Severity of MIS-C fell over time, and most children recovered within 6 months
Key takeaways:
- MIS-C severity decreased over time, but symptoms were more severe for older children.
- Even children with severe symptoms recovered to baseline health within 6 months.
The severity of multisystem inflammatory syndrome in children decreased as the COVID-19 pandemic went on, and most children recovered to their preinfection health within 6 months, according to two recent studies.
“Multisystem inflammatory syndrome in children (MIS-C) remains one of the most serious complications of COVID-19 infection in children,” Dongngan T. Truong, MD, associate professor of pediatrics at Emory University School of Medicine and Children’s Healthcare of Atlanta, and colleagues wrote.
Previous research reported that children with obesity are at risk for more severe symptoms and those with severe neurological symptoms had a higher risk for long-term impairment.
Newly reported data from cases in Germany and Austria showed that symptom severity decreased from 2020 to 2023, and a North American study reported that almost all children recovered without serious morbidity by 6 months after hospital discharge.
More severe among older children
Florens Lohrmann, MD, PhD, from the division of neonatology and pediatric intensive care at the University of Freiburg University Medical Center in Freiburg, Germany,
and colleagues identified trends in the severity of MIS-C — which they referred to as pediatric inflammatory multisystem syndrome — among 920 youth aged younger than 20 years in Germany and Austria between May 28, 2020, and April 30, 2023. They categorized the data by variant waves: the original wave occurred from May 28, 2020, to Feb. 28, 2021; the alpha wave was from March 1 to June 20, 2021; the delta wave took place from June 21 to Dec. 26, 2021; and the omicron wave spanned from Dec. 27, 2021, through April 30, 2023.
During the original wave, 286 MIS-C cases occurred, according to the researchers. Additionally, there were 137 cases during the alpha wave, 292 cases during the delta wave and 205 cases during the omicron wave. The median age during the delta wave was 9 years, whereas the median age for the other three waves ranged from 6 to 7 years.
Lohrmann and colleagues reported that the severity of MIS-C symptoms decreased over time. During the omicron wave, the prevalence of pericardial effusion and pleural effusions were half that of the original wave (19.2% vs. 41.5%; and 24.8% vs. 51.3%, respectively; P < .001 for both). The probability of myocardial disfunction decreased 0.9% per week, and ICU admissions decreased 1.2% per week over the 3-year study period.
However, the researchers also found that older children were at risk for more severe symptoms than younger children. Each year of age increased the probability of myocardial dysfunction by 10.2% and ICU admission by 10.3%. Pleural effusions occurred more frequently in children aged 6 years and older compared with those aged 5 years and younger (43.5% vs. 26.1%; P < .001).
In contrast, the probability of coronary aneurysms fell 8% per year of age, Lohrmann and colleagues found. The probability among all patients decreased from 9.8% during the first wave to 2% during the omicron wave, or 2.6% per week.
“The frequency and severity of (MIS-C) is likely to be related to the declining number of COVID-19-naive individuals over time,” Lohrmann and colleagues wrote. They also hypothesized that increased awareness of the syndrome led to faster diagnosis and treatment, which could have led to milder symptoms.
Recovery after 6 months
Most children with severe cases of MIS-C recovered within 2 weeks, and almost all returned to their pre-infection health by 6 months, Truong and colleagues wrote in JAMA Pediatrics.
They followed the outcomes of 1,204 patients (60.1% boys; median age, 9.1 years; interquartile range [IQR], 5.6-12.7 years) who were hospitalized for MIS-C in North American hospitals from March 2020 to January 2022. They followed up at 2 weeks, 6 weeks and 6 months.
Participants spent a median of 5 days (IQR, 4-8 days) in the hospital, and 62.4% of participants were in the ICU for a median 3 days (IQR, 2-5).
By 2 weeks after discharge, 86.3% of patients reported returning to 90% or more of their baseline health. That proportion rose to 95.1% by 6 months.
Out of 131 patients who had left ventricular ejection fraction (LVEF) percentage below 55% while hospitalized, 93% returned to an LVEF of 55% or higher within 30 days, and all but one patient returned to a normal LVEF by 6 months.
Fifteen patients experienced a coronary aneurysm. Those with small aneurysms — and one patient with a moderate aneurysm — normalized within 6 months, Truong and colleagues wrote. One patient had a large coronary artery aneurysm, which persisted at the 6-week follow-up but was not followed up on after.
“Most patients were critically ill during the acute phase, but 6-month cardiovascular and overall health outcomes were excellent,” Truong and colleagues wrote. “Results suggest that cardiovascular and noncardiovascular morbidities were rare by 6 months after hospital discharge.”
References:
- Lohrmann F, et al. J Pediatr. 2025;doi:10.1016/j.jpeds.2024.114419.
- Truong DT, et al. JAMA Pediatr. 2025;doi:10.1001/jamapediatrics.2024.5466.
Collapse