P3353 - ARMOR Study: Immunogenicity and Safety of Recombinant Spike Protein Vaccine in Patients With Inflammatory Bowel Disease and Liver Transplant Recipients Comparable to Healthy Controls

Ahamed Lazim Vattoth, MD¹, Mary S. Hayney, PharmD, MPH², Freddy Caldera, DO, PhD, MS¹
1University of Wisconsin Hospitals and Clinics, Madison, WI; 2University of Wisconsin-Madison School of Pharmacy, Madison, WI

Introduction: mRNA COVID-19 vaccines are safe in immunosuppressed populations, data on protein-based vaccines remain limited. We evaluated the immunogenicity and safety of Novavax COVID-19 vaccine (NVX-CoV2601) in immunosuppressed patients.

Methods: This single-center, prospective ARMOR study included adults with inflammatory bowel disease (IBD) or solid organ transplant recipients receiving immunosuppressive therapy with ≥3 prior COVID-19 vaccine doses. Participants received one NVX-CoV2601 booster with follow-up at one and six months. Antibody concentrations were measured using anti-spike IgG ELISA and pseudovirus neutralization. The primary outcome was change in antibody concentration from baseline to one month post-vaccination in ARMOR participants. Secondary outcomes included evaluating sustained antibody concentration at 6 months post-immunization, humoral immunogenicity in the ARMOR cohort compared to an age/sex-matched healthy control cohort, adverse events, and safety (IBD flares or transplant rejection). Statistical analyses included paired t-tests for antibody concentration changes and ANCOVA with baseline adjustment for between-group comparisons. GMTs and 95% confidence intervals (CIs) were calculated using log-transformed values.

Results: Twenty-one patients, 18 IBD and 3 liver transplant recipients, were enrolled in ARMOR and compared with 42 age/sex-matched healthy controls (Mean age 47.65, 60% males) (Table 1). In the ARMOR cohort, anti-spike IgG GMT increased significantly post-immunization (22,969 to 66,639 EU/mL at one month; 2.9-fold increase, p=0.001). Healthy controls showed an increase from 54,812 to 129,813 EU/mL (2.4-fold increase; p< 0.001). Neutralizing antibody analysis showed similar trends, with ARMOR participants demonstrating a 3.6-fold increase from baseline (GMT 174.6 ID50 to 628.0 ID50; p=0.002) versus controls' 1.6-fold increase (p=0.001), with no statistically significant difference between groups at day 28 after baseline adjustment (GMTR 1.12; p=0.728). At 6 months, both binding and neutralizing antibodies waned faster in immunosuppressed subjects (GMTR 0.60, p=0.009 for binding; GMTR 0.44, p=0.008 for neutralizing) compared to controls. NVX-CoV2601 was well tolerated, with mild reactogenicity, and was not associated with IBD flares or solid organ rejection.

Discussion: NVX-CoV2601 was safe and immunogenic with similar antibody responses in immunosuppressed patients compared to healthy controls, in contrast to that seen with mRNA vaccines.


Figure: Table 1. Baseline characteristics of immunosuppressed patients enrolled in the ARMOR study.

Disclosures:
Ahamed Lazim Vattoth indicated no relevant financial relationships.
Mary Hayney: GSK Vaccines – Advisor or Review Panel Member, Speakers Bureau. Novavax – Grant/Research Support. Takeda – Grant/Research Support.
Freddy Caldera: GSK – Consultant. GSK – Grant/Research Support. Janssen – Consultant. Novavax – Grant/Research Support.

Ahamed Lazim Vattoth, MD¹, Mary S. Hayney, PharmD, MPH², Freddy Caldera, DO, PhD, MS¹. P3353 - ARMOR Study: Immunogenicity and Safety of Recombinant Spike Protein Vaccine in Patients With Inflammatory Bowel Disease and Liver Transplant Recipients Comparable to Healthy Controls, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.