Neutralizing antibody responses against SARS-CoV-2 in patients with plasma cell disorders who are on active treatment after two doses of mRNA vaccination.

Many patients with plasma cell disorder (PCD) on active treatment with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) require hospitalization, with an increased mortality rate over healthy adults. The FDA approved two mRNA vaccines against SARS-CoV-2: BNT162b2 and mRNA-1273. To assess the efficacy of vaccination in patients with PCD, retrospectively, we identified all patients on active treatment. A total of 149 patients were included. Neutralizing antibodies (NAbs) levels against SARS-CoV-2 adequate, intermediate, and no response were observed in 42%, 32%, and 26%, respectively. Low NAbs were seen in patients on daratumumab combinations or anti-BCMA therapy, low lymphocytes, and low IgG levels. Twenty-three (15%) patients have SARS CoV-2, while 8% required hospitalization, majority of these patients had intermediate or no response based on NAbs levels. Therefore, checking NAbs may be clinically helpful in identifying patients' responses. Further prospective studies should ascertain the value of a third vaccine dose in this population.