GeoVax Next-Generation MVA Vaccine Demonstrates Durable Single-Dose Protection in Preclinical Models

Study Shows Protection Against Highly Pathogenic Clade I Mpox Virus and Durable CD8+ T-Cell Responses

Findings Support GeoVax’s Broader Strategy to Expand the Utility of the MVA Vaccine Platform

ATLANTA, GA - September 21, 2026 (NEWMEDIAWIRE) - GeoVax Labs, Inc. (Nasdaq: GOVX), a clinical-stage biotechnology company developing vaccines and immunotherapies addressing high-consequence infectious diseases and solid tumor cancers, today announced the publication on bioRxiv of preclinical research demonstrating durable single-dose protection using an enhanced Modified Vaccinia Ankara (MVA) vaccine.

The manuscript, “Single-dose Efficacy of a Next-Generation Mpox Vaccine Harnessing an Immunomodulatory Peptide,” reports that a single administration of an enhanced MVA vaccine construct, designated MVA-X, provided durable protection comparable to a conventional two-dose MVA regimen across multiple orthopoxvirus challenge models. Importantly, single-dose MVA-X also protected against lethal challenge with highly pathogenic Clade I mpox virus in a highly susceptible animal model.

The research was conducted in collaboration with investigators at Washington State University and funded by GeoVax. The manuscript is available as bioRxiv preprint here.

Expanding the Potential of MVA to Single-Dose Regimens

MVA has an extensive safety record and is an important vaccine platform for infectious disease preparedness and biosecurity. For mpox prevention, currently recommended MVA-based vaccination generally involves a two-dose regimen. MVA-X was designed to explore the potential for a single-dose approach through modifications intended to enhance the immune response generated following vaccination while preserving the established attributes of the MVA platform.

In the reported studies, a single MVA-X vaccination:

• provided complete protection following lethal and high-dose orthopoxvirus challenge at Days 55, 90 and 150 following vaccination;
• achieved protection comparable to a conventional two-dose MVA regimen;
• restricted viral replication and systemic dissemination;
• generated durable antigen-specific CD8+ T-cell responses despite declining circulating antibody levels; and
• protected highly susceptible animals against lethal challenge with highly pathogenic Clade I mpox virus.

The findings suggest that enhancing early immune priming may provide a strategy for achieving durable MVA-mediated protection following a single vaccination.

David Dodd, Chairman and CEO of GeoVax, commented: “Two-dose administration has long been an accepted characteristic of MVA vaccination. These results provide encouraging preclinical evidence that it may be possible to achieve durable protection following a single vaccination utilizing MVA-X. The potential significance of such an innovation is considerable. During an outbreak, reducing a two-dose regimen to a single vaccination could simplify deployment, accelerate completion of vaccination programs and reduce the logistical burden associated with protecting at-risk populations.”

Dodd continued: “We also view these findings within a broader effort at GeoVax to expand the utility of MVA as a vaccine platform. We are advancing innovations directed at important considerations in vaccine deployment, including dosing, manufacturing and administration. Our objective is to build upon MVA’s established attributes while developing approaches that could make MVA-based vaccines increasingly practical and deployable for global health, outbreak response and biosecurity.”

Mark Newman, Ph.D., Chief Scientific Officer of GeoVax, commented: “These data point toward an innovative approach to augmenting MVA potency and provide support for the important role of the cellular arm of the immune system, particularly CD8-positive T-cell responses, in controlling and clearing orthopoxvirus infection. These findings support further investigation to determine if augmentation of MVA potency can be developed as a next-generation, single-dose vaccine approach for protection against orthopoxvirus infections, with an initial focus on mpox.”

Expanding the Utility of the MVA Platform

The MVA-X research represents one element of GeoVax’s broader effort to advance the utility of MVA-based vaccines. In parallel with approaches designed to improve immunogenicity and potentially enable single-dose vaccination, GeoVax is advancing continuous cell-line manufacturing and evaluating needle-free microarray patch delivery.

Together, these initiatives address three important considerations in vaccine deployment - dosing, manufacturing and administration - with the potential to improve the operational flexibility of MVA-based vaccines, particularly during outbreaks and in global health, resource-constrained and biosecurity settings.

About the Research

The manuscript, “Single-dose Efficacy of a Next-Generation Mpox Vaccine Harnessing an Immunomodulatory Peptide,” reports the preclinical evaluation of MVA-X, an enhanced MVA vaccine construct. A single MVA-X immunization provided durable protection against lethal orthopoxvirus challenge through Day 150 following vaccination and protected against highly pathogenic Clade I mpox virus in a susceptible mouse model.

The studies also demonstrated durable antigen-specific cellular immune responses and provided evidence supporting an important role for CD8+ T cells in viral control.

The research was conducted by investigators from Washington State University and GeoVax and funded by GeoVax. The manuscript is publicly available on bioRxiv under DOI 10.64898/2026.07.31.742137. The manuscript is a preprint and has not been certified by peer review. Findings from preclinical animal studies may not be predictive of results in humans.

About GeoVax

GeoVax Labs, Inc. is a clinical-stage biotechnology company focused on the development of vaccines and immunotherapies addressing high-consequence infectious diseases and solid tumor cancers. GeoVax’s priority program is GEO-MVA, a Modified Vaccinia Ankara (MVA)–based vaccine targeting mpox and smallpox. The program is advancing under an expedited regulatory pathway, with plans to initiate a pivotal Phase 3 clinical trial in the second half of 2026, to address critical global needs for expanded orthopoxvirus vaccine supply and biodefense preparedness. In oncology, GeoVax is developing Gedeptin®, a gene-directed enzyme prodrug therapy (GDEPT) designed to enhance immune checkpoint inhibitor activity. Gedeptin has completed a multicenter Phase 1/2 clinical trial in advanced head and neck cancer and is being advanced into combination strategies, including planned neoadjuvant and first-line settings. GeoVax maintains a global intellectual property portfolio supporting its infectious disease and oncology programs and continues to evaluate strategic partnerships and funding opportunities aligned with its development priorities. For more information, visit 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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