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IDSA’s Recommendations Reinforce GeoVax’s Phase 2 Findings: Robust T-Cell Responses, Cross-Variant Durability, and Favorable Safety Profile in Vulnerable Populations
Atlanta, GA — October 29, 2025 — GeoVax Labs, Inc. (Nasdaq: GOVX), a clinical-stage biotechnology company developing multi-antigen vaccines and immunotherapies, today emphasized how its recently presented Phase 2 clinical data for GEO-CM04S1, first reported at the World Vaccine Congress Europe 2025, align with the new Infectious Diseases Society of America (IDSA) guidelines prioritizing vaccination for immunocompromised individuals.
The IDSA guidance, issued October 17, 2025, concluded that existing COVID-19 vaccines provide only moderate and short-lived protection for immunocompromised patients – with effectiveness against hospitalization ranging from 33% to 56% and waning within two months. The panel called for new vaccine strategies tailored to vulnerable populations, including cancer patients, transplant recipients, and individuals receiving immunosuppressive therapies.
“Immunocompromised Americans are not a niche,” said David A. Dodd, Chairman & CEO of GeoVax. “They are cancer patients, transplant recipients, people with autoimmune disease, and those living with HIV – one in eight adults. They include family members, colleagues and neighbors. Yet mainstream vaccine approaches, heavily centered on mRNA, continue to leave them without durable protection. The new IDSA guidelines reinforce the urgent need for alternatives like GeoVax’s GEO-CM04S1.”
World Vaccine Congress – Data Provide Clinical Reinforcement
At the World Vaccine Congress Europe 2025 in Amsterdam, GeoVax scientific leaders presented new interim data from ongoing Phase 2 studies of GEO-CM04S1, the company’s multi-antigen, MVA-based COVID-19 vaccine designed for immunocompromised populations.
Key findings included:
- Robust T-cell responses to both Spike and Nucleocapsid antigens, exceeding responses seen with mRNA boosters.
- Broad, cross-variant immunity, including activity against Omicron subvariants.
- Favorable safety profile, with only mild-to-moderate adverse events such as injection site reactions, fatigue, and myalgia; no vaccine-related serious adverse events reported.
- In patients with hematologic malignancies post-transplant or CAR-T therapy, breakthrough infections were mild-to-moderate, underscoring the vaccine’s protective potential in highly vulnerable groups.
“These results, together with IDSA’s updated guidance, reinforce the critical need for vaccine platforms that move beyond antibody-only strategies,” said Dodd. “GEO-CM04S1 is designed to provide balanced immunity – antibodies plus durable T-cell responses – which are essential for the immunocompromised patients who remain most vulnerable despite existing vaccination campaigns. The convergence of these guidelines and our clinical findings underscores GEO-CM04S1’s potential to address one of the most critical gaps in COVID-19 prevention.”
GEO-CM04S1: A Vaccine Designed for the Immunocompromised
GeoVax’s GEO-CM04S1 is a multi-antigen, Modified Vaccinia Ankara (MVA)-based COVID-19 vaccine designed to elicit both antibody (humoral) and T-cell (cellular) immune responses. This dual-pathway activation is particularly important for patients who often fail to mount sufficient antibody responses with current mRNA vaccines, including cancer patients on chemotherapy, transplant recipients, and those receiving immunosuppressive therapies.
Key GEO-CM04S1 features include:
- Multi-antigen breadth (Spike + Nucleocapsid proteins) – a design intended to provide broader immunologic coverage and to remain relevant as the virus continues to evolve.
- Durable cellular immunity, critical where antibody responses are weak.
- Alignment with IDSA priorities for transplant, cancer, autoimmune, and HIV patients.
Ongoing trials include Phase 2 studies as a primary vaccine for immunocompromised individuals, including post-transplant and hematologic cancer patients; and, as a booster for patients with chronic lymphocytic leukemia (CLL).
Interim results across these studies consistently demonstrate that GEO-CM04S1 can generate broader, more durable protection than mRNA vaccines, while maintaining a strong safety profile.
Breaking the Single-Platform Dependence
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. GEO-CM04S1 demonstrates how multi-antigen, T-cell–driven approaches can better protect high-risk populations and strengthen pandemic preparedness.
“Protecting the over 40 million immunocompromised Americans is both a moral imperative and a national security necessity,” added Dodd. “With positive clinical data and alignment with IDSA guidance, GeoVax is delivering a differentiated vaccine platform designed to serve those who need it most.”
About GeoVax
GeoVax Labs, Inc. is a clinical-stage biotechnology company developing novel vaccines against infectious diseases and therapies for solid tumor cancers. The Company’s lead clinical program is GEO-CM04S1, a next-generation COVID-19 vaccine currently in three Phase 2 clinical trials, being evaluated as (1) a primary vaccine for immunocompromised patients such as those suffering from hematologic cancers and other patient populations for whom the current authorized COVID-19 vaccines are insufficient, (2) a booster vaccine in patients with chronic lymphocytic leukemia (CLL) and (3) a more robust, durable COVID-19 booster among healthy patients who previously received the mRNA vaccines. In oncology the lead clinical program is evaluating a novel oncolytic solid tumor gene-directed therapy, Gedeptin®, having recently completed a multicenter Phase 1/2 clinical trial for advanced head and neck cancers. GeoVax is also developing a vaccine targeting Mpox and smallpox and, based on recent EMA regulatory guidance, anticipates progressing directly to a Phase 3 clinical evaluation, omitting Phase 1 and Phase 2 trials. GeoVax has a strong IP portfolio in support of its technologies and product candidates, holding worldwide rights for its technologies and products. For more information about the current status of our clinical trials and other updates, visit our website: www.geovax.com.
Forward-Looking Statements
This release contains forward-looking statements regarding GeoVax’s business plans. The words “believe,” “look forward to,” “may,” “estimate,” “continue,” “anticipate,” “intend,” “should,” “plan,” “could,” “target,” “potential,” “is likely,” “will,” “expect” and similar expressions, as they relate to us, are intended to identify forward-looking statements. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. Actual results may differ materially from those included in these statements due to a variety of factors, including whether: GeoVax is able to obtain acceptable results from ongoing or future clinical trials of its investigational products, GeoVax’s immuno-oncology products and preventative vaccines can provoke the desired responses, and those products or vaccines can be used effectively, GeoVax’s viral vector technology adequately amplifies immune responses to cancer antigens, GeoVax can develop and manufacture its immuno-oncology products and preventative vaccines with the desired characteristics in a timely manner, GeoVax’s immuno-oncology products and preventative vaccines will be safe for human use, GeoVax’s vaccines will effectively prevent targeted infections in humans, GeoVax’s immuno-oncology products and preventative vaccines will receive regulatory approvals necessary to be licensed and marketed, GeoVax raises required capital to complete development, there is development of competitive products that may be more effective or easier to use than GeoVax’s products, GeoVax will be able to enter into favorable manufacturing and distribution agreements, and other factors, over which GeoVax has no control.
Further information on our risk factors is contained in our periodic reports on Form 10-Q and Form 10-K that we have filed and will file with the SEC. Any forward-looking statement made by us herein speaks only as of the date on which it is made. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.
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Media Contact:
Jessica Starman