Background: Patients with cancer are at high risk for severe COVID-19 infection. Knowledge regarding efficacy of the mRNA vaccines in actively treated cancer patients is limited as they had been excluded from the pivotal studies of these vaccines. We evaluated humoral and cellular immune response in cancer patients after double vaccination and a booster dose and identified disease- and treatment- related factors associated with a reduced immune response. We also documented number and outcome of breakthrough infections. Patients and methods Patients with metastatic solid malignancies undergoing active treatment were included if they had received two doses of the SARS-CoV-2 mRNA vaccines BNT162b2 or mRNA-1273 and a booster dose. Other causes of immunosuppression and previous COVID-19 infection (positive anti-nucleocapsid titers) were exclusion criteria. Anti-spike antibodies, neutralizing antibodies and T-cell responses were assessed about six months after the two-dose vaccination and four weeks after the booster. Results: Fifty-one patients had pre-booster and 46 post-booster measurements, respectively. Anti-spike titers after two vaccine doses were highly variable and significantly lower in older patients, during treatment with chemotherapy compared to targeted and endocrine treatments and in patients with low CD4+ or CD19+ cell counts. The booster dose led to a significant increase in anti-spike and neutralizing antibodies, achieving almost uniformly high titers, irrespective of baseline and treatment factors. Cellular immune response was also significantly increased by the booster, however generally more stable and not influenced by baseline factors and treatment type. Seventeen patients (33%) experienced breakthrough infections, none required hospital care or died from COVID-19. Conclusions: An mRNA-vaccine booster dose is able to increase humoral and cellular immune response and to overcome the immunosuppressive influence of baseline and treatment factors in cancer patients. Breakthrough infections were uniformly mild in this vaccinated high-risk population.

Fuente: ESMO Open
Available online 24 August 2022, 100587