CD19 and Miyoshi myopathy: Albeit the size of the current MM patient cohort was too small to statistically evaluate a predictive score for the likelihood of vaccination response, we suggest to be particularly alert in patients in whom two or more of the following factors apply: (a) age ≥ 65 years, (b) ≤ 30 CD19+ B lymphocytes/μL, (c) current anti-CD38-directed treatment, (d) any quadruplet treatment and (e) not in deep remission (≤PR).