Immunogenicity of anti-SARS-CoV-2 Comirnaty vaccine in patients with lymphomas and myeloma who underwent autologous stem cell transplantation

This prospective cohort study assessed the humoral and cell-mediated immune responses and clinical efficacy of anti-SARS-CoV-2 vaccination in adult patients with hematological malignancies (HMs). A total of 365 patients who completed a two-dose mRNA vaccine regimen were analyzed. Seroconversion was observed in 82% of patients, with reduced rates in those receiving anti-CD20 therapy (4%), BTK inhibitors (42%), JAK2 inhibitors (68%), and daratumumab-based regimens (69%). Among initially seronegative individuals, 37% achieved seroconversion following a booster dose. Cellular immunity, evaluated by ELISpot and flow cytometry, demonstrated the presence of spike-specific memory T cells, albeit at lower levels in seronegative patients. During a median follow-up of 269 days, 8% of patients developed breakthrough SARS-CoV-2 infections, with a significantly increased incidence following the emergence of the Omicron variant. Seropositivity after vaccination was associated with a reduced risk of breakthrough infection, whereas cellular immunity did not exhibit a significant protective effect. Comparative analysis of vaccinated and pre-vaccination cohorts revealed significantly lower rates of severe disease (10% vs. 33%), hospitalization (17% vs. 50%), and shorter disease duration (16 vs. 22 days) in vaccinated individuals. These findings confirm reduced vaccine immunogenicity in patients with HMs, particularly those undergoing active treatment, while demonstrating a protective effect against severe COVID-19 outcomes.