MIS-C cases more severe in second wave, study finds
Patients with multisystem inflammatory syndrome in children experienced more severe illness during a second wave of cases compared with the first, according to a study published in The Pediatric Infectious Disease Journal.
The CDC defines multisystem inflammatory syndrome in children (MIS-C) as a condition in any patient aged 21 years or younger who presents with fever, laboratory evidence of inflammation, evidence of clinically severe illness requiring hospitalization, with two or more organs involved, who has no alternative plausible diagnosis and has tested positive for current or recent SARS-CoV-2 infection, or reports exposure to a suspected or confirmed case of COVID-19. A similar syndrome also can occur in adults.
Ashraf S. Harahsheh, MD, FACC, FAAP, a cardiologist at Children's National Hospital in Washington, and colleagues managed two pediatric cohorts of patients with MIS-C, following surges of COVID-19 cases in the U.S.
The first cohort consisted of 43 patients who were hospitalized between March and October 2020, whereas the second was composed of 63 patients hospitalized between November and April 2021.
“We’ve now seen three distinct waves of MIS-C since the beginning of the pandemic, each wave following national spikes in cases,” Roberta DeBiasi, MD, chief of pediatric infectious diseases at Children's National and a coauthor of the study, said in a news release.
“Kids in the second wave cohort had potentially experienced intermittent and/or repeated exposures to the virus circulating in their communities,” DeBiasi said. “In turn, this may have served as repeated triggers for their immune system, which created the more severe inflammatory response.”
Among a total of 106 patients from both waves, 46% were female, 54% were Black, 39% were Hispanic and the median age was 8.4 years (range, 4.7-13.4). No underlying medical conditions were found in 80 patients (75%).
Compared with patients hospitalized during the first wave, patients hospitalized during the second wave included a higher proportion of older children (21% vs. 5%), and they were more likely to present with shortness of breath (18% vs. 3%) but less likely to test positive for SARS-CoV-2 (16% vs. 49%).
Participants hospitalized during the second wave were also more likely than those in the first wave to require vasopressors (73% vs. 51%) and were less likely to use only a high-flow nasal cannula (10% vs. 26%).
“Despite the increased degree of clinical severity and laboratory abnormalities in the [second] cohort, no significant differences were noted comparing wave 2 and wave 1 cohorts,” the authors wrote.
Perspective
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It is interesting to evaluate how a new clinical entity may evolve over time in the pandemic. These authors looked at two time periods of MIS-C surges that closely followed significant COVID-19 waves in their community.
I was a bit surprised to see differences in the patients presenting with MIS-C at each time point. Specifically, those from wave 2 were older (aged >15 years), and in many ways appeared sicker. They were more likely to complain of dyspnea, require ionotropic support, require bilevel positive airway pressure or other more intensive ventilatory support, have higher troponin and brain natriuretic peptide values.
Despite the evidence of higher severity, there were no significant long-term differences, such as coronary aneurysms or length of stay. Apart from age, the groups were similar in sex and racial/ethnic background, so these would not explain the differences.
I was tempted to invoke differences in the SARS-CoV-2 variants in circulation, but these data predate the delta variant surge.
I also would consider increased recognition as we learned more about MIS-C (the second wave was less likely to be SARS-CoV-2-PCR positive), but the authors point out that a standard protocol was used.
A possible explanation offered was that repeated exposure to SARS-CoV-2 in the community as time went on could have sensitized the patients in wave 2 to have a more robust reaction.
This could be an area for further study. However, we have not seen rampant recurrence of MIS-C in children previously afflicted. A case report was recently published to that effect as well.
Further, there is no contraindication to vaccinating after MIS-C. If immune stimulation from repeat infection was a concern, it might also be seen with vaccination, and it has not been to date.
I think MIS-C will be a fascinating area of investigation for years to come.
References:
Buddingh EP, et al. Pediatr Infect Dis J. 2021;doi:10. 1097/INF.0000000000003280.
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