GeoVax Labs, Inc., a biotechnology company developing human vaccines, announces a major step forward in the development of a vaccine candidate for protection against Zika virus (ZIKV). Preliminary testing in a highly rigorous challenge model showed the candidate, GEO-ZM02, provided 100% protection to mice infected with a lethal dose of ZIKV. The study was funded by a grant from the U.S. Centers for Disease Control and Prevention (CDC), which also provided technical assistance.


During testing, mice were given a single-dose vaccination of GEO-ZM02 into muscle tissue, then infected with a lethal dose of ZIKV administered directly to the brain. All vaccinated mice survived whereas all unvaccinated mice died within a week of infection.

Currently, no vaccine or medicine exists for the prevention or treatment of ZIKV infection.

GEO-ZM02 uses GeoVax’s proven MVA vaccine platform that has been shown to be safe and to induce durable antibody and T-cell responses in multiple human clinical trials for GeoVax’s prophylactic HIV vaccine. Using the same platform, GeoVax’s Ebola vaccine has been shown to protect 100% of rhesus monkeys against death caused by Ebola virus upon a single-dose vaccination.

Farshad Guirakhoo, PhD, GeoVax’s Chief Scientific Officer, stated, “We believe our MVA vaccine platform potentially offers the best solution to safely protect at-risk populations from the Zika epidemic. GEO-ZM02 not only has the potential of a single-dose vaccine, which is practical to combat epidemics in resource-strained countries, but also does not bear the risk of enhancing other flavivirus infections, such as dengue virus, in vaccinated subjects. This phenomenon, called Antibody Dependent Enhancement (ADE) of infection, has been the topic of recent publications, and is a safety concern for other Zika vaccines under development that utilize the structural Envelope (E) protein of ZIKV for their vaccine construct. Our vaccine is based on the non-structural-1 (NS1) protein of ZIKV, which is not involved in ADE. Moreover, the NS1 protein is abundantly secreted into the blood of a ZIKV-infected individual and plays a critical role in flavivirus acquisition by mosquitoes by overcoming the immune barrier of the mosquito midgut. Therefore, GEO-ZM02 should not only protect populations against ZIKV infections but could also block further transmission of ZIKV from humans back to its mosquito host.”

Robert McNally, PhD, GeoVax’s President and Chief Executive Officer, commented, “The results from this study are impressive and give us confidence in pressing forward with our Zika vaccine program and engaging with potential partners for clinical trials and commercialization. With the proper resources, we anticipate that human clinical trials could commence within 18 months.”