GeoVax Labs, Inc. announced positive initial safety and immune response findings from its Phase 2 clinical trial at one month following administration of its Covid-19 vaccine, GEO-CM04S1. The trial, evaluating GEO-CM04S1 as a heterologous booster in 63 healthy adults who had previously received the Pfizer or Moderna mRNA vaccine (ClinicalTrials.gov Identifier: NCT04639466), was fully enrolled at the end of Sept 2023. The study is designed to evaluate the safety and immunogenicity of two GEO-CM04S1 dose levels.

The trial remains blinded to dose of vaccine received, with study subjects being followed for a total of one year. To date, there have been no serious adverse events, and adverse events were in line with other routine vaccinations. The immunological responses measured throughout the study period include both neutralizing antibodies against SARS-CoV-2 variants and specific T-cell responses.

Consolidated data from all subjects tested one-month post-vaccination, documented statistically significant increases in neutralizing antibody responses against multiple SARS-CoV-2 variants, ranging from the original Wuhan strain through Delta and Omicron XBB 1.5; additional testing against the JN.1 variant is underway. GEO-CM04S1 is a next-generation Covid-19 vaccine based on GeoVax?s MVA viral vector platform, which supports the presentation of multiple vaccine antigens to the immune system in a single dose. GEO-CM04S1 encodes for both the spike (S) and nucleocapsid (N) antigens of SARS-CoV-2 and is specifically designed to induce both antibody and T-cell responses to those parts of the virus less likely to mutate over time.

The more broadly functional engagement of the immune system is designed to protect against severe disease caused by continually emerging variants of Covid-19. Vaccines of this format should not require frequent and repeated modification or updating. These latest findings lend support to previously published findings in cell transplant patients of the ability of GEO-CM04S1 to stimulate functional antibody responses against a broad array of evolving SARS-CoV-2 virus variants (Chiuppesi et al, Vaccines, Sept 2023).