GeoVax's COVID-19 Vaccine Shows Promise for Immunocompromised Patients Following IDSA Guidelines

The Infectious Diseases Society of America's recent guidelines highlighting the limitations of current COVID-19 vaccines for immunocompromised patients align with emerging clinical data from GeoVax Labs' investigational vaccine candidate GEO-CM04S1. The IDSA guidance, issued October 17, 2025, concluded that existing vaccines provide only moderate and short-lived protection for immunocompromised individuals, with effectiveness against hospitalization ranging from 33% to 56% and waning within two months. This recognition underscores the urgent need for alternative vaccine approaches tailored to vulnerable populations including cancer patients, transplant recipients, and individuals receiving immunosuppressive therapies.

GeoVax presented interim Phase 2 clinical data for GEO-CM04S1 at the World Vaccine Congress Europe 2025 that directly addresses these concerns. The data demonstrated robust T-cell responses to both Spike and Nucleocapsid antigens, exceeding responses seen with mRNA boosters. The vaccine also showed broad, cross-variant immunity including activity against Omicron subvariants, along with a favorable safety profile characterized by only mild-to-moderate adverse events such as injection site reactions, fatigue, and myalgia. Importantly, no vaccine-related serious adverse events were reported across the studies.

David A. Dodd, Chairman & CEO of GeoVax, emphasized the significance of these findings, noting that immunocompromised Americans represent approximately one in eight adults, including cancer patients, transplant recipients, people with autoimmune disease, and those living with HIV. The convergence of IDSA's updated guidance and GeoVax's clinical data highlights the critical need for vaccine platforms that move beyond antibody-only strategies. GEO-CM04S1 is designed to provide balanced immunity through both antibody and durable T-cell responses, which are essential for populations that remain vulnerable despite existing vaccination campaigns.

GEO-CM04S1 represents a multi-antigen, Modified Vaccinia Ankara-based COVID-19 vaccine specifically engineered to elicit both humoral and cellular immune responses. This dual-pathway activation is particularly important for patients who often fail to mount sufficient antibody responses with current mRNA vaccines. The vaccine's multi-antigen breadth, targeting both Spike and Nucleocapsid proteins, is intended to provide broader immunologic coverage and remain relevant as SARS-CoV-2 continues to evolve. Ongoing Phase 2 trials are evaluating GEO-CM04S1 as both a primary vaccine for immunocompromised individuals and as a booster for specific patient populations including those with chronic lymphocytic leukemia.

The implications of this development extend beyond immediate patient care to broader public health considerations. While mRNA vaccines were pivotal in the early pandemic response, their limitations in durability, breadth, and performance in immunocompromised populations highlight the risks of relying on a single platform approach. GEO-CM04S1 demonstrates how multi-antigen, T-cell-driven strategies can better protect high-risk populations and strengthen overall pandemic preparedness. For more information about GeoVax's clinical programs, visit https://www.geovax.com. The positive clinical data combined with alignment from leading infectious disease authorities positions GEO-CM04S1 as a potential solution to one of the most critical gaps in COVID-19 prevention for vulnerable populations worldwide.