FAQ: GeoVax's Multi-Antigen COVID-19 Vaccine for Immunocompromised Patients

What is GEO-CM04S1 and how does it differ from current COVID-19 vaccines?

GEO-CM04S1 is a synthetic, next-generation COVID-19 vaccine candidate that co-expresses both spike (S) and nucleocapsid (N) antigens using GeoVax’s MVA vector platform, designed to induce both antibody and T-cell responses, unlike current vaccines that primarily target only the spike protein.

What were the key findings presented at the World Vaccine Congress Europe 2025?

The presentations highlighted that GEO-CM04S1 elicits strong T-cell responses to both Spike and Nucleocapsid antigens exceeding mRNA boosters, shows a favorable safety profile comparable to mRNA vaccines with only mild-to-moderate adverse events, and demonstrates broad, durable immunity including responses against Omicron subvariants.

Why is this vaccine particularly important for immunocompromised patients?

Current ‘one-size-fits-all’ vaccines have limitations for immunocompromised populations, and GEO-CM04S1 is designed to fill this critical gap by providing broader, more durable protection against severe COVID-19 for vulnerable patients who are not adequately protected by existing vaccines.

What safety data was reported for GEO-CM04S1 in immunocompromised patients?

In patients with hematologic malignancies post-transplant or CAR-T cell therapy, GEO-CM04S1 showed only mild-to-moderate treatment-emergent adverse events (predominantly injection site reactions, fatigue, and myalgia), with no vaccine-related serious adverse events, myocarditis, or pericarditis reported to date.

Which patient populations are being studied in the Phase 2 clinical trials?

GEO-CM04S1 is being evaluated in three Phase 2 trials: as a primary vaccine for immunocompromised individuals (post-transplant and hematologic cancer patients), as a booster for chronic lymphocytic leukemia patients, and as a durable booster for healthy adults previously immunized with mRNA vaccines.

What advantages does GEO-CM04S1 offer over current vaccine approaches?

The multi-antigen approach provides broader specificity, increased memory, and potentially longer-lasting protection that could reduce the need for frequent vaccine reformulations, while generating robust T-cell responses that exceed those induced by mRNA boosters.

When and where were these results presented?

The results were presented at the World Vaccine Congress Europe 2025, held October 13-16 at the RAI Amsterdam Convention Centre in Amsterdam, Netherlands, by GeoVax’s senior scientific leadership including Chief Scientific Officer Mark J. Newman, PhD and Chief Medical Officer Kelly T. McKee, Jr., MD, MPH.

What is the current development status of GEO-CM04S1?

GEO-CM04S1 is currently in three Phase 2 clinical trials and is GeoVax’s lead clinical program, with ongoing studies continuing to show consistent safety profiles across different patient populations.