TNFRSF17 and amyotrophic lateral sclerosis: To establish if the ALS-BCMA biomarker could also be used to predict oral vaccine memory IgA responses, we compared ALS-BCMA responses after primary oral ETVAX vaccination with the ALS-IgA antibody responses of booster vaccinated volunteers 13–23 months later (n = 25, Supplementary Figure 1B).