Abstract
This study reports the relationship between CD38(+) regulatory T cells (Tregs) and messenger RNA coronavirus disease 2019 (mRNA-COVID-19) vaccination in 60 patients with plasma cell dyscrasia. Patients treated with anti-CD38 monoclonal antibodies (mAbs) had significantly lower CD38(+) Tregs than those not treated (0.9 vs. 13.2/μl). Late-responders, whose antibody titres increased from weeks 4-12 after the second vaccination, had significantly lower CD38(+) Treg counts than non-late-responders (2.5 vs. 10.3/μl). Antibody titres in patients with lower CD38(+) Treg levels were maintained from weeks 4-12 but decreased in those with higher CD38(+) Treg levels. Therefore, depletion of CD38(+) Tregs by anti-CD38 mAbs may induce a durable response to mRNA-COVID-19 vaccination.