CD40LG and Japanese encephalitis: At 1 month after vaccination with CD-JEV, > 40% of children had a JE IgM positive or equivocal result on testing their serum, suggesting that if a child in a JE-endemic area presents with encephalitis, has JE IgM antibody in serum, and recently has been vaccinated with CD-JEV, consideration should be given to the antibody being vaccine related, and alternate etiologies of encephalitis should be sought.