ABSTRACT
BACKGROUND: It was shown that immunocompromised patients have significantly reduced immunologic responses to COVID-19 vaccines. The immunogenicity of COVID-19 vaccine/infection in patients with solid tumors is reduced. We evaluated the immunologic response to COVID-19 and/or the BNT162b2 mRNA COVID-19 vaccine among cancer patients on active treatments and reviewed previous literature to identify subgroups that may require third vaccination. PATIENTS AND METHODS: Anti-SARS-CoV-2 S1/S2 antibodies were measured in a cohort of 202 cancer patients on active treatment with chemotherapy (96), immunologic (52), biologic (46), and hormonal (12) treatments for early (n = 66, 32.7%) or metastatic disease (n = 136, 67.3%). Of those, 172 had received two vaccine doses, and 30 had COVID-19 infection (20/30 also received one dose of vaccine). Specific anti-S receptor-binding domain antibodies were further measured in patients with equivocal anti-S1/S2 results. RESULTS: Among cancer patients, the SARS-CoV-2 antibody response rate was 89.1% (180/202) after COVID-19 vaccination or infection and 87.2% (150/172) in patients after vaccination without a history of COVID-19, compared with 100% positive serologic tests in a control group of 30 health care workers (P < 0.001). Chemotherapy treatment was independently associated with significantly reduced humoral response to infection or vaccination, with an 81.3% response rate, compared with 96.2% in patients on other treatments (P = 0.001). In vaccinated patients on chemotherapy, the positive response rate was 77.5%. In a multiple regression model, a neutralizing antibody titer (>60 AU/ml) was more likely with immunotherapy (odds ratio 2.44) and less likely with chemotherapy (odds ratio 0.39). CONCLUSIONS: Overall, both COVID-19 vaccine and natural infection are highly immunogenic among cancer patients. Our study, however, identifies those under chemotherapy as significantly less responsive, and with lower antibody levels. These findings justify close virological and serological surveillance along with consideration of these patients for booster (third dose) vaccine prioritization, as new highly spreading SARS-CoV-2 variants emerge.