West Nile virus (WNV) is transmitted to humans by mosquitoes. It first appeared in North America in 1999. Elderly people are more susceptible than younger people to developing severe WNV infection and its complications, which include meningitis (bacterial infection of the membranes covering the brain and spinal cord) and encephalitis (brain inflammation).
There currently are no licensed vaccines to prevent WNV infection in humans, but researchers at the NIAID Vaccine Research Center (VRC) developed a promising candidate. A VRC study showed that a three-dose regimen of its modified DNA vaccine was safe and well-tolerated in 30 human volunteers, half of whom were between 18 and 50 years old; the other half were between 51 and 65 years old. Importantly, the majority of the participants produced T-cell and neutralizing antibody responses to the vaccine, a key measure of effectiveness.
The T-cell responses produced by the vaccine were of a greater magnitude than those produced by an earlier-generation WNV vaccine. Furthermore, the antibody responses seen in the older age group were similar in frequency, magnitude, and duration compared to the antibody responses in the younger group, suggesting that the vaccine may be effective in protecting older people from severe WNV infection.
Reference: Ledgerwood JE, Pierson TC, Hubka SA, Desai N, Rucker S, Gordon IJ, Enama ME, Nelson S, Nason M, Gu W, Bundrant N, Koup RA, Bailer RT, Mascola JR, Nabel GJ, Graham BS; VRC 303 Study Team. A West Nile virus DNA vaccine utilizing a modified promoter induces neutralizing antibody in younger and older healthy adults in a phase I clinical trial. J Infect Dis. 2011 May 15;203(10):1396-404.
Last Updated January 08, 2013
Last Reviewed January 08, 2013