Background/Purpose: Most children who contract SARS-CoV-2 are asymptomatic or mildly symptomatic, but a subset subsequently develop the hyperinflammatory condition called multisystem inflammatory syndrome in children (MIS-C). There has been hesitation to vaccinate children with a history of MIS-C against SARS-CoV-2 over concerns that hyperinflammation may recur. As part of our post-MIS-C follow-up care, we have advocated for COVID-19 vaccination. We aimed to determine the frequency of COVID-19 vaccination among the cohort of patients with a history of MIS-C diagnosed at our institution.

Methods: Patients who presented May 2020-October 2022 with an acute febrile illness that fulfilled the 2020 Centers for Disease Control and Prevention MIS-C case definition were included. During outpatient subspecialty care following hospitalization, patients with a history of MIS-C were counseled on and encouraged to receive COVID-19 vaccination after 90 days from discharge. Charts were retrospectively reviewed to identify patients vaccinated against SARS-CoV-2. COVID-19 vaccine findings were confirmed using a state immunization registry.

Results: Vaccines were reviewed for 294 of 295 patients diagnosed with MIS-C: one patient died prior to discharge. 99 of 294 patients (34%) received at least one dose of COVID-19 vaccine after MIS-C diagnosis. Vaccinated patients were 58% male, and initiated vaccination at a mean of 10.8 years of age (range 3-19 years) and at 8.8 months post-MIS-C hospitalization (range 20 days-24.4 months). 90 of 99 patients are partially vaccinated: 13 received one dose of vaccine, 60 received 2 doses, and 17 received 3 or more doses of monovalent COVID-19 vaccine. 9 are fully vaccinated, including one 3-year-old who completed a 3-dose primary series and 3 patients who had 3 doses of monovalent vaccine prior to a bivalent booster.All patients received mRNA vaccine; 99% of doses (193 of 194) were BNT162b2. No patients have re-presented with a recurrence of MIS-C or any other hyperinflammatory condition over a mean of 11.3 months of follow-up since last vaccination (range 18 days-23.1 months). In our cohort, 15 of 295 patients (5%) received a COVID-19 vaccination at a time prior to the onset of MIS-C; all but one had evidence of prior or current SARS-CoV-2 infection at MIS-C presentation, either by nucleic acid amplification and/or nucleocapsid serology. 7 of these 15 patients have received subsequent doses of COVID-19 vaccine, and none have reported recurrence of hyperinflammation (mean 8.2 months since last dose, range 2.8-13.8 months).

Conclusion: SARS-CoV-2 vaccination is well-tolerated by children with a history of MIS-C. This is reassuring as SARS-CoV-2 becomes endemic and annual vaccination against SARS-CoV-2 is considered. Work is in progress to prospectively monitor patients with a history of MIS-C for vaccine reactogenicity and immune activation following SARS-CoV-2 vaccination.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/sars-cov-2-vaccination-of-children-with-a-history-of-multisystem-inflammatory-syndrome/