Multisystem Inflammatory Syndrome Following SARS-CoV-2 Vaccination in Two Children

This report presents 2 pediatric cases of multisystem inflammatory syndrome in children and adults (MIS-C/A) post severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination (MIS-V). Both children presented with MIS-V within 6 weeks of receiving their first and only dose of Pfizer-BioNTech's SARS-CoV-2 vaccine. The first patient had symptoms of MIS-C/A with peri-myocarditis and shock, and the second 1 had classic Kawasaki disease features. Both responded well to intravenous immunoglobulins and/or systemic corticosteroids. Both children were positive only for SARS-2-CoV antispike (S) (and not for antinucleocapsid [NC]) antibodies consistent with a postvaccine, and not a postinfection, event. Surveillance for rare adverse events following immunization should continue, especially now that SARS-CoV-2 vaccination is approved in the 5 to 11 year age group that has had the highest risk of developing MIS-C post SARS-CoV-2 infection. Our patients did not receive any further SARS-CoV-2 vaccines. Our report highlights the importance of measuring differentiating antibodies (anti-S and anti-NC) that can be used within a specific timeframe to help determine if a patient has MIS-V post vaccine (only anti-S present), or MIS-C/A post SARS-CoV-2 infection (both anti-S and anti-NC present).

Automated summary

This report describes two pediatric cases of multisystem inflammatory syndrome in children and adults (MIS-C/A) following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination (MIS-V). Both children developed MIS-V within six weeks of receiving their first and only dose of Pfizer-BioNTech's SARS-CoV-2 vaccine. One patient exhibited symptoms of MIS-C/A with peri-myocarditis and shock, while the second patient showed classic features of Kawasaki disease. Both children responded well to treatment with intravenous immunoglobulins and/or systemic corticosteroids. Antibody testing revealed that both children were positive for SARS-2-CoV antispike (S) antibodies only, indicating a post-vaccination event rather than a post-infection event. The importance of continued surveillance for rare adverse events following immunization, especially in the 5-11 year age group at highest risk for MIS-C after SARS-CoV-2 infection, is emphasized. This report also highlights the significance of measuring differentiating antibodies (anti-S and anti-NC) within a specific timeframe to determine whether a patient has MIS-V post-vaccine (only anti-S present) or MIS-C/A post SARS-CoV-2 infection (both anti-S and anti-NC present).