Patient Population

This retrospective observational study was approved by the institutional review board of the University of Texas Southwestern Medical Center (Dallas, TX, USA). Patients diagnosed with a myeloid or lymphoid malignancy that had a quantitative SARS-CoV-2 IgG spike antibody measured between December 2020 and November 2021 after receiving two doses of the Moderna or Pfizer/BioNTech SARS-CoV-2 vaccine were included in the study. Inhouse testing for a quantitative IgG antibody titer detection was performed for the majority (N=40) of the patients in accordance with the manufacturer’s package insert (AdviseDX SARS-CoV-2 IgG II/ SARS-CoV-2 IgG II Quant assay, Abbott Alinity i platform, Abbott Laboratories, Chicago, IL, USA) (5). Briefly, SARS-CoV-2 antigen-coated microparticles bind to the IgG antibodies that attach to the virus’s spike protein. Subsequently, an anti-human IgG conjugate is added and the degree of chemiluminescence is measured, reflecting the quantity of IgG present. The remaining patients had send-out testing performed either using an immunoassay that uses a recombinant protein that represents the nucleocapsid virus antigen (Roche Elecsys® anti-SARS-CoV2 reagent assay, Roche Diagnostics, Indianapolis, IN, USA (N=16)) or an assay that selects the receptor-binding domain of the S1 spike antigen to detect neutralizing IgG antigens (Atellica® IM SARS-CoV-2 IgG (COV2G) Siemens Healthcare Diagnostics, Terrytown, NY, USA (N=4)). Vaccine response was defined as having a positive quantifiable spike IgG antibody titer per the laboratory reference range.