Immune responses after one versus two Influenza A/B vaccinations in patients with multiple myeloma.

Seasonal Influenza A/B vaccination is routinely administered in patients with Multiple Myeloma (MM) given their disease-and therapy-associated immunosuppression and risk of infection. Previous data show poor seroconversion rates after one vaccination with an increase to ~ 60% after boosting while the impact of multiple lines of therapy remains unclear. Accordingly, we performed a retrospective single-center study assessing immune responses after single or prime-boosting vaccination in 71 patients with MM treated at our institution during the 2019/20 season. Overall, 63.3% of patients with MM achieved sufficient responses after one or two Influenza A/B vaccinations. In patients receiving a prime-boost approach, significantly higher serological titers but no significant increase in responder rates were observed after the boost vaccination. Complete or very good partial remission and no immunoparesis were identified as independent predictors of sufficient serological response by multivariate regression analysis and responders were characterized by high CD19 B-cell and CD4 T-cell counts. Patients achieving a sufficient response only after the prime-boost approach showed significantly shorter time since high-dose chemotherapy and autologous stem-cell transplantation (HDC-ASCT). Together, this study suggests that single vaccination against Influenza A/B might be sufficient for patients with MM while a prime-boost approach might be necessary for patients with recent HDC-ASCT.