Abstract
The effects of SARS-CoV-2 vaccination in children with previous multisystem inflammatory syndrome (MIS-C) are not well understood. In this study, we aimed to assess immune responses to SARS-CoV-2 vaccination in children over the age of 12 years with previous MIS-C and compare them to healthy children. Three children with previous MIS-C and four healthy children received two doses of the BNT162b2 vaccine. Blood was collected before the first dose, one week after the first dose, one week after the second dose and three weeks after the second dose. All participants had detectable SARS-CoV-2 spike IgG before vaccination. Spike binding and neutralising antibody activity increased after the first vaccine dose with no differences between children with a history of MIS-C and healthy children. Serum inflammatory cytokines and whole blood immune gene profiles did not resemble acute MIS-C and there were no differences in these between the two groups at any timepoint. All participants gained a robust SARS-CoV-2-specific T cell response by three weeks after the second dose. A transient increase in SARS-CoV-2-specific CD4 T cells expressing TCR Vβ21.3, a non-specific T cell subset previously found to be enriched in patients with MIS-C, was demonstrated in two of the children with previous MIS-C but none of the healthy children. Together, these data demonstrate that vaccination is effective at boosting SARS-CoV-2-specific immune responses in a small group of children with previous MIS-C, and that it does not induce inflammatory cytokine or gene expression responses resembling acute MIS-C. Although larger-scale studies are needed to confirm these findings, the present evidence supports SARS-CoV-2 vaccination in children with previous MIS-C.