Abstract CT259: Comprehensive humoral and cellular immune assessments to SARS-CoV-2 (wild type, delta and omicron) following two- and three-dose vaccination schedule in a large adult cancer population: SerOzNET study: placeholder abstract
Authors: Segelov Eva , Body Amy , Luong Vi , Lopez Veronica Aedo , Lal Luxi , Abdulla Hesham , Turville Stuart , Niang Zin , Opat Stephen , McCuaig Robert , Lineburg Katie , Rao Sudha , Smith Corey , MacIntyre Raina , Ahern Elizabeth 
Published: June 2022

Abstract
Background: Defining cancer and treatment-related factors which influence protection against COVID-19 following vaccination are important given the worse outcomes following infection in this group. Sophisticated and detailed studies which go beyond a single measure are required particularly with correlation to multiple disease and treatment factors. This study cohort is unique due to (a) very low prior COVID-19 infection at time of sampling (July-Nov 2021), (b) vaccines studied were BNT162b2 (Pf) given 3 weeks apart or ChAdOx1 (AZ) spaced 12 weeks (dose 1, 2) (c) most participants then received a third dose 2 months later (heterologous for AZ).
Methods: SerOzNET (ACTRN12621001004853) enrols Australian blood and solid cancer patients prior to vaccination, with serial blood analyses and qualitative measures. We measured neutralizing antibodies (nAb) against SARS-CoV-2 wild type (wt) and variants of concern delta and omicron, quantitative S-protein IgG antibody level (Abbott), and T-cell correlates (interferon-g, tumour necrosis factor-a, interleukins 2/4/5/13) and epigenetic profiling at baseline and 3-4 weeks post dose 1, 2 +/- 3.
Results: 379 participants were included, median age 58 years (IQR 47-66) and 60% female. 30% participants had hematological malignancies with the remainder solid organ cancers. 90% patients were on current systemic cancer treatment (most commonly chemotherapy in 41%, chemoimmunotherapy or immunotherapy in 20%). In 331 patients where treatment intent was recorded, 47% was palliative. Only one patient had known prior COVID-19 infection. Of the initial 94 participants who received Pf vaccination, median (IQR) neutralizing antibody titre 4 weeks following dose 2 was 80 (40-160) for SARS-CoV-2 wt and 40 (0-80) for delta variant.
Conclusion: Neutralizing antibody titres in this Australian cancer population following Pf vaccination appear lower than those reported elsewhere such as CAPTURE study (Fendler et al, 2021), possibly related to shorter interdose interval. Preliminary data highlights low nAb titres as expected in haematology patients but also in some cases with treatment not traditionally associated with immunosuppression such as hormonal therapy. These results will be updated in February 2022 with third dose, AZ and omicron variant data.
Citation Format: Eva Segelov, Amy Body, Vi Luong, Veronica Aedo Lopez, Luxi Lal, Hesham Abdulla, Stuart Turville, Zin Niang, Stephen Opat, Robert McCuaig, Katie Lineburg, Sudha Rao, Corey Smith, Raina MacIntyre, Elizabeth Ahern. Comprehensive humoral and cellular immune assessments to SARS-CoV-2 (wild type, delta and omicron) following two- and three-dose vaccination schedule in a large adult cancer population: SerOzNET study: placeholder abstract [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT259.