ABSTRACT
Background: Vaccination is considered essential for individual protection during the SARS-CoV-2-pandemic. The efficacy of the current vaccines in MM-patients is unknown. Aim: To determine seroconversion rates and antibody levels in MM about 3 and 6 months after the second dose of the vaccine BNT162b2. Methods: Patients with symptomatic MM without prior COVID19 were eligible. We measured levels of SARS-CoV-2-spike-and-nucleocapsid-antibodies (AB) by electro-chemiluminescence-immunoassay and extracted clinical data from hospital records. Results: 101±14 (mean±SD) days after the second vacccination sero-conversion (anti-spike-[S]-AB ≥0.8 U/l) was detectable in 54/59 (91.5%) MM-patients and 21/21 controls, with lower concentrations in MM-patients (median 166 U/l versus 929 U/l, p<0.001). The percentage of individuals with anti-S <250 U/l was 9% (1/11) for vaccination during "watch-and-wait", 39% (12/31) during maintenance and 82% (14/17) during (re-)induction. No patient developed COVID19. Details regarding the vaccination-response according to different clinical factors are shown in the table. The anti-S-concentration fell significantly (mean-45%, range-100%-+42%, p<0.001) at follow-up (mean 88±11 days after the first measurement;performed in MM-patients only). Conclusions: Most MM-patients responded to the BNT162b2 vaccine, but often with lower concentrations of anti-S three months after the second vaccination, which additionally declined over time. Besides age and markers of immunosupression, treatment-modalities seem to affect the vaccination-response more than disease-related factors. Daratumumab did not influence the anti-S-concentration in our cohort. In order to determine the anti-S threshold for a third vaccination, regular assessment of the vaccination response in all MM patients, regardless of treatment, seems advisable.