Humoral Immune Response Following SARS-CoV-2 mRNA Vaccination and Infection in Pediatric-Onset Multiple Sclerosis.

OBJECTIVE: Currently, there are no data available on SARS-CoV-2 vaccine responses in pediatric-onset multiple sclerosis (POMS), and little is known about the course of SARS-CoV-2 infection in this age group. We therefore investigated humoral immune responses after COVID-19 vaccination and/or infection in POMS. METHODS: We retrospectively analyzed seroconversion rates and SARS-CoV-2-specific antibody levels in 30 POMS and one pediatric CIS patient treated with no disease-modifying therapy (no DMT), immunomodulatory DMT (IM-DMT), or immunosuppressive DMT (IS-DMT) from two Austrian MS centers. RESULTS: The median age at MS onset was 15.39 years (interquartile range [IQR]: 1.97). The median age at the first COVID-19 vaccination was 17.43 years (IQR: 2.76). After two vaccine doses, seroconversion (≥0.8 BAU/ml) was reached in 25 of 28 patients (89.3%). All patients with no DMT or IM-DMT generated robust immune responses to vaccination (seroconversion: no DMT: 6/6, IM-DMT: 7/7 [100%]; median titers: no DMT: 2075 BAU [IQR: 1268.50], IM-DMT: 2500 BAU [IQR: 0]). In the IS-DMT group, seroconversion was achieved in 12 of 14 patients (80%), and median titers were 50.8 BAU (IQR 254.63). Titers were significantly higher in no DMT versus IS-DMT (P = 0.012) and in IM-DMT versus IS-DMT (P = 0.001). Infection with SARS-CoV-2 occurred in 11 of 31 patients, and symptoms were mild in all cases. One relapse occurred after infection, but no relapses were documented after vaccination. CONCLUSIONS: Generally, mRNA vaccinations were well tolerated in POMS patients with and without DMT. Immune response was significantly reduced in patients treated with IS-DMT. No unexpected adverse events or relapses related to vaccinations were observed.