1559O Efficacy and toxicity of BNT162b2 vaccine in cancer patients

Ben-Aharon, I.; Waldhorn, I.; Holland, R.; Peer, A.; Halberthal, M.; Goshen - Lago, T. G.

Background: Efficacy and safety profile of COVID-19 vaccines had been acquired from phase III studies. Nevertheless, cancer patients were not represented in these trials. In 1/2021 mass vaccination of high-risk population, including cancer patients, was initiated in Israel. We aimed to prospectively evaluate efficacy, immunogenicity and safety of BNT162b2 vaccine in cancer patients. Methods: Cancer patients on active treatment were prospectively enrolled following first dose of BNT162b2 or after a second dose. Serum was collected after each dose and additionally in case of seronegativity. An age-matched cohort of healthcare workers served as controls. Questionnaires regarding sociodemographics and adverse reactions were employed at serum collection. FDA-approved assay was used to assess IgG at all time-points. Patients’ electronic medical records were reviewed for documentation of COVID-19 infection, blood counts, liver enzymes and imaging studies. Results: The study included 232 cancer patients and 261 controls. Following first dose 29% of patients were seropositive compared with 84% of controls (p<0.001). Following second dose seropositive rate reached 86%. Rate per 1000-person days after first dose were 12.5 for patients and 48.5 for controls. Chemotherapy reduced immunogenicity (OR 0.41 (95%CI 0.17-0.98). In seronegative patients, rate of documented leukopenia reached 39%. No COVID19 cases were documented throughout the study period except two cases following the first dose. Reported adverse events resembled former published studies. Conclusions: Our results indicate the BNT162b2 appear to be safe and effective in cancer patients. There is a pronounced lag in antibody production compared with non-cancer controls, however seroconversion occurred in most patients after the second dose. Future real-world data is warranted to determine the long-term efficacy of the vaccine with regard to type of anti-cancer treatment. Legal entity responsible for the study: The authors. Funding: ICRF. Disclosure: All authors have declared no conflicts of interest.