Enzyme immunoassay has become the method of choice for rapid serodiagnosis of virus infections by detection of specific IgM antibodies and has been frequently applied in a quantitative assay format to monitor immune response to vaccines.35 Serologic diagnosis is generally accomplished by measurement of IgM antibodies by ELISA, hemagglutination inhibition (HI), and neutralization.2 Here, we have analyzed the humoral immune response against YFV after vaccination over long and short periods of time. The gene discussed is CD40LG; the disease is viral infectious disease.