Patients with cancer are at an increased risk for severe coronavirus disease of 2019, thus data on the safety and efficacy of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines are essential. We conducted this prospective study of patients with cancer vaccinated with BNT162b2 and monitored for antibody response and safety. The aim was to evaluate the rate of seropositivity and define predictors for non-reactive immune response. Furthermore, we evaluated the frequency and the severity of adverse events.
The study included patients with solid tumours undergoing anticancer treatment and immunocompetent health-care workers serving as controls. Serum titres of the receptor-binding domain (RBD) immunoglobulin G (IgG) and neutralising antibodies were measured 2-4 weeks after each vaccine dose.
The analysis included 129 patients, of which 70.5% patients were metastatic. Patients were treated with chemotherapy (55%), immunotherapy (34.1%), biological agents (24.8%), hormonal treatment (8.5%) and radiotherapy (4.6%), that were given either alone or in combinations. The seropositivity rate among patients with cancer and controls was 32.4% versus 59.8% (p < 0.0001) after the first dose and 84.1% versus 98.9% (p < 0.0001) after the second dose, respectively. Median RBD-IgG titre was lower among patients than controls (p < 0.0001). Patients who were seronegative after the second dose had significantly more comorbidities than that with patients with seropositivity (77.8% vs 41.1%, respectively, p = 0.0042).
Adequate antibody response after BNT162b2 vaccination was achieved after two doses but not after one dose, in patients with cancer vaccinated during anticancer therapy.

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