Longitudinal SARS-CoV-2 mRNA vaccine-induced humoral immune responses in cancer patients.

Longitudinal studies of SARS-CoV-2 vaccine-induced immune responses in cancer patients are needed to optimize clinical care. In a prospective cohort study of 366 (291 vaccinated) patients, we measured antibody levels [anti-spike (IgG-(S-RBD)) and anti-nucleocapsid immunoglobulin] at three timepoints. Antibody level trajectories and frequency of breakthrough infections were evaluated by tumor type and timing of treatment relative to vaccination. IgG-(S-RBD) at peak response (median=42 days after dose 2) was higher (p=0.002) and remained higher after 4-6 months (p=0.003) in patients receiving mRNA-1273 compared to BNT162b2. Patients with solid tumors attained higher peak levels (p=0.001) and sustained levels after 4-6 months (p<0.001) compared to those with hematologic malignancies. B-cell targeted treatment reduced peak (p=0.001) and sustained antibody responses (p=0.003). Solid tumor patients receiving immune checkpoint inhibitors before vaccination had lower sustained antibody levels than those who received treatment after vaccination (p=0.043). Two (0.69%) vaccinated and one (1.9%) unvaccinated patient had severe COVID-19 illness during follow-up. Our study shows variation in sustained antibody responses across cancer populations receiving various therapeutic modalities with important implications for vaccine booster timing and patient selection.