A comprehensive evaluation of humoral immune response to second and third SARS-CoV-2 mRNA vaccination in patients with malignant lymphoma

More information is needed regarding the efficacy of SARS-CoV-2 mRNA vaccines in immunocompromised populations, including patients with malignant lymphoma. This study aimed to evaluate humoral responses to the second and third mRNA vaccine doses in 165 lymphoma patients by retrospective analysis of serum SARS-CoV-2 spike protein antibody (S-IgG) titers. Patients with S-IgG titers ≥ 300, 10–300, and ≤ 10 binding antibody units (BAU)/mL were defined as adequate responders, low responders, and non-responders, respectively. S-IgG titers > 10 BAU/mL were considered to indicate seroconversion. After the second dose, 56%, 16%, and 28% of patients were adequate responders, low responders and non-responders, respectively. Multivariate analysis revealed that being an adequate responder after the second dose was associated with receiving the vaccine > 12 months after last chemotherapy, total peripheral lymphocyte count of ≥ 1000/µL, estimated glomerular filtration rate of ≥ 50 mL/min/1.73 m2, and vaccine type (mRNA-1273). After the third dose, patients had significantly higher S-IgG titers and a greater proportion achieved seroconversion. With this third dose, 26% of second-dose non-responders achieved seroconversion and 68% of second-dose low responders became adequate responders. Subsequent SARS-CoV-2 mRNA vaccinations may elicit an immune response in immunocompromised patients who do not initially respond to vaccination.