Measles is a highly contagious disease characterized by a prodromal illness of fever, coryza, cough, and conjunctivitis followed by the appearance of a generalized maculopapular rash. Despite the availability of an effective and safe live attenuated vaccine, measles remains a cause of continuing outbreaks in Japan. Measles often accompanies diverse complications, including pneumonitis, otitis media, and central nervous system involvement. Neurological complications of measles includes ADEM, MIBE, and SSPE. MIBE and SSPE have unfavorable prognosis, which are caused by persistent infection of particular mutants of measles virus (MV) in brain. In SSPE patients, measles antibody titer increase in cerebrospinal fluid and serum. Primary vaccine failure and secondary vaccine failure may be a major cause of outbreaks in Japan, therefore, promotion of vaccination should be emphasized. 2 doses vaccination methods began in Japan in 2006, and supplementary vaccination program at 12 and 18 years old begins from 2008. Protection level of antibody titer varies according to the antibody measurement methods. NT provides the best correlate for protection from infection, however, needs complicated procedure. PA is chosen for the surveillance method in Japan, and 1:128 or over seems protection level. To protect health-care associated infection of MV, all health care worker under 35 years old should be vaccinated if not have adequate immunity.