Six-Month Humoral and Cellular Immune Response to the Bnt162b2 Mrna Covid-19 Vaccine Booster in the Patients with Solid Tumors on Active Treatment: Focus on Variants of Concern (Vocs)

ABSTRACT

Background: The role and the durability of immunogenicity of the 3rd dose of vaccine against COVID-19 variants of concern (VOCs) in cancer patients remains to be elucidated. The aim of this study is to evaluate the immunogenicity of the 3rd dose of the SARS-CoV-2 BNT162b2 mRNA vaccine in triggering both the humoral and the cell-mediated immune response in the patients with solid tumors undergoing active treatment 6 months after booster Methods: We have prospectively evaluated kinetics of humoral and cellular immune response elicited by booster BNT162b2 anti-SARS-CoV-2 vaccine dose up to 6 months. Samples were collected at the enrollment (T0), 21 days after the booster (T1) and 6 months after (T2). Sera were tested for Spike trimeric IgG (cut off 33.8 BAU/mL) and SARS-CoV-2 neutralizing antibodies (NT Abs;cut off 110), T-cell response against Spike protein was detected by IFNgamma release assay (IGRA from Euroimmun). Result(s) One-hundred patients (36F/50M;median age 65, range 26-89) were included in the study. In 9 subjects, a COVID-19 infection was reported before the administration of the 1st dose of vaccine. Preliminary analyses were performed in a cohort of 79 previously unexposed subjects. The 3rd dose was administered at median 176 days (range 91-281) after the 1st dose. At T0 anti-S IgG response was median 170 (IQR 67.8-421.4) BAU/mL and it increased to median 2080 (IQR 2080-2080) BAU/mL at T1;a decrease of response was observed at T2 (median 1605 IQR 822-2080 BAU/mL). Overall, 11/79 (13.9%) patients were negative at baseline and 10/11 reached positive level of response at T1. Only 2 subjects were negative for serological response at T2. A similar trend was observed for SARS-CoV-2 NTAbs. In 65 patients we compared NT Abs levels reached against wild type (WT) strain, Delta and Omicron variants at T2. Median response against WT strain was 1320 (IQR 140-1640) while it decreased to 180 (IQR 120-1320) and 110 (IQR <110-140) against Delta and Omicron variants (p value 0.08 and <0.001, respectively). Overall, 4/65 (6.2%) patients were negative for WT SARS-CoV-2 NT Abs while 6/65 (9.2%) and 17/65 (26.2%) were negative for Delta and Omicron SARSCoV- 2 NT Abs, respectively. Conclusion(s) Preliminary data suggest an enhanced immunogenicity elicited by booster in cancer patients, also against variant strains, even if a decrease NT Abs level was observed against Omicron. T-cellular response and multivariable analysis on demographic/clinical data will be presented at the meeting.