Archive for September 6th, 2012

Does Yellow Fever Vaccine Protect Against West Nile Virus?

Thursday, September 6, 2012 // Uncategorized

West Nile Virus is in the news a lot these days:


West Nile Virus Cases Up 25% in Past Week


Nearly 2000 human cases of West Nile virus have been reported to the CDC so far this year, representing an increase of about 25% in the past week, the agency reports in its weekly update. Nearly 90 people have died from the disease in 2012.


There is currently no commercially available vaccine against the virus for humans, although one is available for animals (horses and geese).  Since West Nile Virus and Yellow Fever virus belong to the same family, Flaviviruses, there was interest several years ago as to whether being vaccinated against Yellow Fever virus protected against West Nile virus.  the answer seems to be no.

West Nile virus infection and serologic response among persons previously vaccinated against yellow fever and Japanese encephalitis viruses.


Division of Vector-Borne Infectious Diseases (DVBID), National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 80521, USA. [email protected]


It is hypothesized that previous heterologous flaviviral exposure may modulate clinical illness among persons infected with West Nile virus (WNV). Little is known about the serological response in such persons. In summer 2003, a WNV outbreak occurred in Colorado, the location of the Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases (DVBID). DVBID employees, most previously vaccinated with yellow fever virus (YFV) or Japanese encephalitis virus (JEV) vaccines, were studied to determine whether previous vaccination affected symptom development among those subsequently infected with WNV during the outbreak, as well as their serological response. Serum samples collected in December 2003 and previously banked samples were tested using the plaque reduction neutralization test (PRNT) against WNV, Saint Louis encephalitis virus, dengue- 4 virus, JEV, and YFV. Specimens shown to have WNV antibody by PRNT were tested by IgM and IgG enzymelinked immunosorbent assays (ELISAs). Ten (9%) of 113 serosurvey participants had WNV neutralizing antibody titers in December 2003. PRNT titers from previous specimens showed that one of the ten had seroconverted to WNV before 2003. Of the remaining nine participants, seven reported illness in the summer of 2003, two of which were unvaccinated and five previously vaccinated. In the December 2003 specimens, five persons previously unvaccinated or vaccinated only against YFV had a fourfold or greater neutralizing titer with WNV than with other flaviviruses, whereas no persons previously vaccinated against JEV or JEV and YFV showed a similar difference in neutralizing titers. Eight of nine persons infected in 2003 had negative or indeterminate WNV MAC-ELISA results in the December 2003 sample; the ninth person was vaccinated against YFV one month previously, and was also YFV positive by MAC-ELISA. We conclude that previous flaviviral vaccination does not markedly affect the development of WNV fever and that the IgM antibody response in patients without neuroinvasive WNV disease is transient.

[PubMed – indexed for MEDLINE]
 There is no more recent information available, but human vaccines are being tested.  Whether they will be effective and whether the economics of a new vaccine development will make it feasible remains to be seen. 



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