Single-Dose MVA-X Vaccine Shows Durable Protection Against Lethal Clade I Mpox in Preclinical Study

GeoVax Labs, Inc. (Nasdaq: GOVX) announced on September 21, 2026, the publication of preclinical research on bioRxiv demonstrating that a single dose of an enhanced Modified Vaccinia Ankara (MVA) vaccine, designated MVA-X, provides durable protection against lethal orthopoxvirus challenges, including highly pathogenic Clade I mpox virus. The findings, which have not yet been peer-reviewed, suggest that MVA-X could simplify vaccination campaigns by reducing the need for a two-dose regimen, a significant shift for a platform long associated with two-dose administration.

The study, titled “Single-dose Efficacy of a Next-Generation Mpox Vaccine Harnessing an Immunomodulatory Peptide,” was conducted in collaboration with Washington State University and funded by GeoVax. In multiple animal models, a single MVA-X immunization provided complete protection at Days 55, 90, and 150 following vaccination, comparable to a conventional two-dose MVA regimen. Importantly, it also protected highly susceptible animals against lethal challenge with Clade I mpox virus, a strain associated with more severe disease. The vaccine restricted viral replication and systemic dissemination, and generated durable antigen-specific CD8+ T-cell responses even as circulating antibody levels declined, pointing to a key role for cellular immunity in controlling orthopoxvirus infection.

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.” He added that during an outbreak, reducing a two-dose regimen to a single vaccination could simplify deployment, accelerate completion of vaccination programs, and reduce logistical burdens. Dodd also noted that the findings support GeoVax’s broader strategy to expand the utility of the MVA platform, with ongoing innovations in dosing, manufacturing, and administration.

Mark Newman, Ph.D., Chief Scientific Officer of GeoVax, emphasized the importance of CD8+ T-cell responses in controlling and clearing orthopoxvirus infection. “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,” he said. The results warrant further investigation to determine if MVA-X can be developed as a next-generation, single-dose vaccine for orthopoxvirus infections, with an initial focus on mpox.

The MVA-X research is part of GeoVax’s broader effort to advance MVA-based vaccines. In parallel, the company is developing continuous cell-line manufacturing and evaluating needle-free microarray patch delivery. Together, these initiatives address dosing, manufacturing, and administration to improve operational flexibility, particularly in outbreaks and resource-constrained settings. GeoVax’s priority program, GEO-MVA, is advancing under an expedited regulatory pathway with plans to initiate a pivotal Phase 3 clinical trial in the second half of 2026. The full manuscript is available as a preprint on bioRxiv under DOI 10.64898/2026.07.31.742137. For more information, visit www.geovax.com. The original release can be viewed on www.newmediawire.com.