ABSTRACT
BACKGROUND: Activity and safety of the SARS-CoV-2 BNT162b2 vaccine in actively treated patients with solid tumors is currently unknown. METHODS: We conducted a retrospective study of 326 patients with solid tumors treated with anticancer medications to determine the proportion of cancer patients with immunogenicity against SARS-CoV-2 following 2 doses of the BNT162b2 vaccine. The control group comprised 164 vaccinated healthy adults. Anti-SARS-CoV-2 S immunoglobulin G antibodies were measured using a level greater than 50 AU/mL as a cutoff for seropositivity. Information on adverse effects was collected using a questionnaire. All statistical tests were 2-sided. RESULTS: Most patients (205, 62.9%) were treated with chemotherapy either alone or with additional therapy; 55 (16.9%) were treated with immune checkpoint inhibitors and 38 (11.7%) with targeted therapy alone; 28 (8.6%) received other combinations. The vaccine was well tolerated, and no severe side effects were reported. Among patients with cancer, 39 (11.9%) were seronegative compared with 5 (3.0%) of the control group (P = .001). Median immunoglobulin G titers were statistically significantly lower among patients with cancer compared with control (931 AU/mL vs 2817 AU/mL, P = .003). Seronegativity proportions were higher in the chemotherapy-treated group (n = 19; 18.8%) compared with the immune checkpoint inhibitor-treated patients (n = 5; 9.1%) and with those treated with targeted therapy (n = 1; 2.6%) (P = .02). Titers were also statistically significantly different among treatment types (P = .002). CONCLUSIONS: The BNT162b2 vaccine is safe and effective in actively treated patients with cancer. The relatively lower antibody titers and lower proportion of seropositive patients, especially among chemotherapy-treated patients, call for continuing the use of personal protective measures in these patients, even following vaccination.