The BNT162b2 vaccine was shown to be highly effective in reducing the risk of COVID-19 infection in healthy individuals and patients with chronic disease. However, there are little data regarding its efficacy in patients treated for cancer. We analyzed the humoral response following vaccination with the second dose of BNT162b2 in 140 patients with solid malignancies who were receiving anti-cancer therapy at the time of vaccination and 215 participants who had not been diagnosed with cancer. Multivariate analysis was performed, followed by matching the two groups by age, gender and days from vaccination. The humoral response in the cancer patient group was significantly lower than in the non-cancer group: 20/140 seronegative (14.3%) vs. 3/215 (1.4%), p < 0.001; median IgG levels 2231 AU/mL (IQR 445-8023) vs. 4100 (IQR 2231-6774) p = 0.001 respectively. The odds ratio for negative serology results in cancer patients adjusted by age and gender was 7.35 compared to participants without cancer. This effect was observed only in chemotherapy treated patients: 17/73 seronegative (23.3%) vs. 3/215 (1.4%), p < 0.001; median IgG 1361 AU/mL vs. 4100, p < 0.001 but not in patients treated with non-chemotherapeutic drugs. Reduced immunogenicity to COVID-19 vaccine among chemotherapy-treated cancer patients, raises the need to continue exercising protective measures after vaccination in these patients.
Keywords: COVID-19 vaccine; SARS-CoV-2; antibody response; cancer; chemotherapy; immunotherapy.