Out of the 77 JE vaccine recipients, only one (vaccine recipient #73) exhibited neutralizing activity against DENV-1 in the serum samples collected both before and after JE vaccination (BHK cells, PRNT50 DENV1PRE = 160, PRNT50 DENV1POST = 160; FcγR-expressing BHK cells, PRNT50 DENV1PRE = 40, PRNT50 DENV1POST = 40). The gene discussed is FCGR2A; the disease is Japanese encephalitis.