Seropositivity and neutralising antibodies at six months after BNT162b2 vaccination in patients with solid tumours

Aim: Patients with cancer are at an increased risk for severe coronavirus disease of 2019. We previously reported initial findings from a single centre prospective study evaluating antibody response after BNT162b2 vaccine, showing that adequate antibody response was achieved after two doses, but not after one, in patients with cancer vaccinated during anticancer therapy. Herein, we report a follow-up study, evaluating antibody response six months after the second vaccine dose. Methods: 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) IgG and neutralising antibodies (Nabs) were measured approximately six months after the second vaccine dose. Complete blood count values were collected and evaluated as predictors for antibody response. Results: The analysis included 93 patients with cancer (66.7% metastatic). Six months after the second vaccine dose (mean 176 ± 20 days), seropositivity rate among patients and controls was 83.9% versus 96.3% (p = 0.0001), respectively. Median RBD-IgG titre was lower among patients compared with controls (2.3 versus 3.2, p = 0.0002). Among seropositive individuals, median Nabs titre was similar between patients with cancer and controls (p = 0.566). Among patients with cancer, lymphocyte and neutrophil counts were not correlated with either RBD-IgG or Nabs titres. Conclusions: Seropositivity rates and RBD-IgG titre at six months after second BNT162b2 vaccine dose are lower among patients with cancer compared with healthy controls. However, Nabs titre is similar, suggesting a comparable protection among seropositive individuals. Lymphocyte count is not predictive of antibody response.