Factors Associated with Seroconversion after COVID-19 Vaccination in Patients with Hematologic Malignancies
Authors: Ollila Thomas A. , Masel Rebecca , Reagan John L , Paiva Kimberly , Lu Shaolei , Rogers Ralph , Zayac Adam , Taher Rashida , Yakirevich Inna , Niroula Rabin , Barth Peter , Olszewski Adam J. 
Published: November 2021

Abstract
Background: Recent studies reported low rates of seroconversion response to COVID-19 vaccination in patients (pts) with hematologic malignancies (HMs). Vaccine choice among the 3 FDA-authorized products (BNT162b2/Pfizer-BioNTech, mRNA-1273/Moderna, or Ad26.COV2.S/J&J), prior therapy, and disease-specific factors may affect seroconversion. Addressing these factors may improve seroconversion rates and identify pts at risk of severe COVID-19 infection despite vaccination.
Methods: We conducted a retrospective study of adults with HMs vaccinated in our center between 2/2021 and 7/2021, excluding pts with prior COVID-19 infection. Seroconversion was assessed by the qualitative SARS-CoV-2 Total Antibody Test (IgG/IgM against Receptor Binding Domain [RBD], Wondfo USA, Willowbrook, IL). A subset of samples was tested by the semi-quantitative Abbott AdviseDx SARS-CoV-2 IgG II assay (IgG against RBD). For univariate associations (UVA) we used Fisher's exact test for categorical variables, and fractional polynomial fits for continuous variables to examine non-linearity. Multivariable analysis (MVA) used a robust Poisson model reporting risk ratio (RR) with 95% confidence intervals (CI).
Results: Among 239 eligible pts, median age was 70 (range, 28-94), and 112 (47%) were female. HMs included aggressive B-cell lymphomas (n=74, 31%), indolent B-cell lymphomas (n=52, 22%), chronic lymphocytic leukemia (CLL, n=30, 13%), other lymphomas (n-19, 8%), plasma cell neoplasms (n=43, 18%), and myeloid cancers (n=21, 9%); 140 pts (59%) received BNT162b2/Pfizer, 74 (31%) mRNA-1273/Moderna, and 23 (10%) Ad26.COV2.S/J&J vaccines (2 pts had undetermined vaccine type). HM was active in 100 pts (42%), whereas 108 (45%) pts were in remission after treatment, and 31 (13%) on watchful waiting (WW, never treated); 141 (59%) had a prior exposure to an anti-B-cell monoclonal antibody, and 22 (9%) prior stem cell transplantation.
Overall, 99 pts (41%; binomial 95% CI, 35-48%) showed post-vaccination seroconversion upon testing at median 10 weeks from first vaccine. Seroconversion was significantly less frequent among pts with lymphomas compared with plasma cell or myeloid neoplasms (overall P=.020; Fig A). It was also less frequent after prior anti-B-cell antibody exposure (29% vs 59%, P&lt;.0001; Fig. B), and in those with active disease (28%, vs 49% for remission [P=.0027], vs 58% for WW [P=.0045]; Fig. C). Furthermore, seroconversion was significantly more frequent after mRNA-1273/Moderna vaccine (57%) compared with BNT162b2/Pfizer (36%, P=.006) or Ad26.COV2.S/J&J (22%, P=.004; Fig. D). It was not associated with age (Fig. E), WBC (Fig. G), or time from vaccination (Fig. I), but was significantly higher with increased lymphocyte count (P&lt;.0001; Fig F) and time elapsed from last chemotherapy (P=.0039; Fig. H).
In a MVA (Fig. J), vaccination with mRNA-1273 remained significantly associated with higher rate of seroconversion compared with BNT162b2 (RR=0.59; 95%CI, 0.44-0.79) or Ad26.COV2.S (RR=0.35; 95%CI, 0.16-0.77). Higher seroconversion rate was also associated with remission (RR=1.98; 95%CI, 1.42-2.76) or WW status (RR=1.72; 95%CI 1.02-2.89) compared with active disease, and higher lymphocyte count. Exposure to anti-B-cell antibodies remained associated with lack of seroconversion (RR=0.66; 95%CI, 0.44-0.99). Seroconversion was borderline less frequent in CLL than lymphomas, and higher with plasma cell or myeloid disorders. Results were similar in the subset of pts (n=191) with prior treatment, adjusting for time from last chemotherapy(data not shown).
The anti-COVID-19 IgG titers on semiquantitative test (n=47, all after mRNA-based vaccines) were also lower in pts with active disease compared with those in remission (P=.065) or under WW (P=.028), and in those with prior anti-B-cell antibody (P=.0095).
Conclusions: Pts with HMs demonstrate overall low rates of seroconversion after vaccination against COVID-19, particularly when they have active disease or are on/after B-cell depleting monoclonal antibody therapy. The mRNA vaccines (particularly mRNA-1273) appear to have elicited superior responses compared with the adenovirus-based product. Pts with active HMs or those within 2 years of last therapy should be particularly aware of the risk of infection despite vaccines and should be considered for strategies to enhance anti-COVID-19 immunity regardless of age.
Figure 1 Figure 1.

Disclosures
Olszewski: TG Therapeutics: Research Funding; PrecisionBio: Research Funding; Celldex Therapeutics: Research Funding; Acrotech Pharma: Research Funding; Genentech, Inc.: Research Funding; Genmab: Research Funding.