Evaluation of vaccine-induced antibody responses against SARS-CoV-2 in multiple myeloma patients from the northeastern region of Mexico

OBJECTIVE: To evaluate immunoglobulin G antibody responses against Severe Acute Respiratory Syndrome Coronavirus 2 in multiple myeloma patients in the northeastern region of Mexico following different COVID-19 vaccination regimens. METHODS: This retrospective study included 33 multiple myeloma patients, and 28 healthy controls vaccinated with mRNA (BNT162b2, mRNA-1273) or adenovector (AZD1222) vaccines. Anti-spike receptor-binding domain (RBD) and anti-nucleocapsid immunoglobulin G levels were measured. Laboratory parameters, including monocyte and lymphocyte counts and serum-free light chains, were analyzed. Statistical comparisons used ANOVA, Kruskal-Wallis, and logistic regression. RESULTS: No significant differences in anti-spike receptor-binding domain immunoglobulin G levels were observed between multiple myeloma patients and healthy controls after one vaccine dose. Multiple myeloma patients who received ≥3 doses showed higher anti-spike receptor-binding domain immunoglobulin G levels compared to single-dose recipients. Anti-nucleocapsid antibodies (indicative of prior subclinical infection) were detected in 51.5% of multiple myeloma patients and correlated with elevated anti-spike receptor-binding domain levels. Patients in the third anti-spike immunoglobulin G quartile (10,427.9-23,954.0 AU/mL) had higher monocyte counts compared with patients in the lower quartiles. No correlations were found between anti-spike immunoglobulin G and lymphocyte counts, serum proteins, or gamma globulins. Abnormal kappa/lambda light chain ratios did not impair antibody responses in nucleocapsid-positive patients. CONCLUSION: Multiple myeloma patients achieved comparable immunoglobulin G responses to healthy controls after one vaccine dose, with enhanced responses following ≥3 doses. Subclinical infections may augment humoral immunity. Elevated monocyte counts are indicative of innate immune activation following the administration of the vaccine. These findings support prioritizing booster doses for multiple myeloma patients despite immunosuppressive therapies.