The U.S. Centers for Disease Control and Prevention (CDC) has reported a significant shift in the epidemiology of Clade I mpox in the United States, with evidence pointing to likely sustained domestic transmission of the Clade Ib subclade. In its September 25 update, the CDC confirmed more than 60 laboratory-confirmed Clade I mpox cases across at least 20 states. Since August, an increasing proportion of these cases have occurred among individuals with no recent international travel or known links to recent travelers. Cases with presumed domestic transmission have now been reported in more than 10 jurisdictions, which the CDC said indicates a “likely transition to sustained Clade Ib transmission in the United States.”
While the CDC continues to assess the risk from the Clade I outbreak as low for most people in the United States, it notes that additional travel-related and domestically acquired Clade Ib cases are expected. This development marks a notable change from earlier surveillance: as recently as August, the CDC reported that sustained Clade Ib transmission had not been detected in the U.S. during 2024–2025. The 2022 global mpox outbreak, including the large U.S. outbreak, was caused by Clade IIb, and Clade I mpox has historically been associated with more severe disease and higher mortality. However, recent Clade Ib cases in high-income countries have generally involved relatively mild illness, highlighting the importance of distinguishing changing epidemiology from immediate risk.
GeoVax Labs, Inc. (Nasdaq: GOVX), a clinical-stage biotechnology company developing vaccines against infectious diseases and therapies for solid tumor cancers, highlighted the CDC’s update. David Dodd, Chairman and CEO of GeoVax, commented, “CDC’s latest assessment represents an important change in the epidemiology of Clade Ib mpox in the United States. While the risk to the general population remains low, presumed domestic transmission across multiple jurisdictions reinforces the importance of continued surveillance, vaccination of appropriate at-risk populations and sustained preparedness.” Dodd continued, “Preparedness should not begin when an infectious-disease threat becomes a crisis. The appropriate time to strengthen vaccine capacity, diversify sources of supply and establish scalable manufacturing infrastructure is before those capabilities are urgently needed.”
GeoVax is advancing GEO-MVA, a Modified Vaccinia Ankara (MVA)-based vaccine candidate for mpox and smallpox. Following formal guidance from the European Medicines Agency, the company is pursuing an expedited clinical development pathway that allows it to proceed directly to a pivotal Phase 3 immunobridging study, comparing immune responses generated by GEO-MVA with those of the licensed MVA-BN comparator. GeoVax expects to initiate the 500-participant study in the fourth quarter of 2026, with results expected in mid-2027. The company believes GEO-MVA can become an important strategic preparedness asset by supporting diversified vaccine supply, scalable manufacturing capacity, and greater supply resilience.
The evolving mpox landscape follows other public-health preparedness actions, including updated CDC vaccination recommendations for certain U.S. travelers at increased risk and international initiatives to strengthen access to mpox vaccines. Globally, Clade I outbreaks have continued in Central and Eastern Africa since late 2023, with subsequent geographic expansion, including transmission in parts of Europe and introductions into the United States. As Dodd concluded, “Low risk to the general population today and the need for long-term preparedness are not contradictory. CDC’s latest assessment illustrates why preparedness must anticipate changes in infectious-disease transmission rather than react to them after they occur.” For more information, visit www.geovax.com.
