Low Spike Antibody Levels and Impaired BA.4/5 Neutralization in Patients with Multiple Myeloma or Waldenstrom's Macroglobulinemia after BNT162b2 Booster Vaccination.

Patients with symptomatic monoclonal gammopathies have impaired humoral responses to COVID-19 vaccination. Their ability to recognize SARS-CoV-2 Omicron variants is of concern. We compared the response to BNT162b2 mRNA vaccinations of patients with multiple myeloma (MM, n = 60) or Waldenstrom's macroglobulinemia (WM, n = 20) with healthy vaccine recipients (n = 37). Patient cohorts on active therapy affecting B cell development had impaired binding and neutralizing antibody (NAb) response rate and magnitude, including several patients lacking responses, even after a 3rd vaccine dose, whereas non-B cell depleting therapies had a lesser effect. In contrast, MM and WM cohorts off-therapy showed increased NAb with a broad response range. ELISA Spike-Receptor Binding Domain (RBD) Ab titers in healthy vaccine recipients and patient cohorts were good predictors of the ability to neutralize not only the original WA1 but also the most divergent Omicron variants BA.4/5. Compared to WA1, significantly lower NAb responses to BA.4/5 were found in all patient cohorts on-therapy. In contrast, the MM and WM cohorts off-therapy showed a higher probability to neutralize BA.4/5 after the 3rd vaccination. Overall, the boost in NAb after the 3rd dose suggests that repeat vaccination of MM and WM patients is beneficial even under active therapy.