As West Nile Virus Cases Rise, Vaccine Still Far Off

Nancy A. Melville

September 17, 2012

In This Article

Experimental Vaccines in the Works

Experimental West Nile virus vaccines that have been in the works in recent years have run the gamut from inactivated/killed vaccines and live attenuated vaccines to subunit vaccines, vectored vaccines, and DNA vaccines.

Among the vaccines that have advanced the most is the ChimeriVax-WN02 (Sanofi-Pasteur), a live attenuated chimeric vaccine produced by "insertion of the genes encoding the pre-membrane and envelope proteins of West Nile virus (strain NY99) into the yellow fever 7D vaccine virus," according to its developers.

Results of a randomized, double-blind, placebo-controlled phase 2 trial on the vaccine, published online September 7 in Vaccine, showed safety and high immunogenicity achieved in healthy participants aged 50 years and older at 4 different dose levels.

Dr. William Schaffner

Although representing a step in the right direction, the nature of a phase 2 study still leaves many questions unanswered, said infectious disease specialist William Schaffner, MD.

"We have to remember how these studies are done. This study included adults in general good health, which meant it excluded those with serious underlying illness, who just happen to be the ones at the highest risk for West Nile virus," Dr. Schaffner, chair of the Department of Preventive Medicine at the Vanderbilt University School of Medicine in Nashville, Tennessee, told Medscape Medical News.

Those interested in seeing how the vaccine would perform in such patients may not want to hold their breath, however. According to lead author Gustavo Dayan, MD, medical director of clinical development at Sanofi-Pasteur in Swiftwater, Pennsylvania, there are currently no plans for phase 3 trials of the vaccine.