There are no compulsory vaccinations required to travel to Japan but there are a few recommended ones just to be on the safe side. If you travel to Japan anywhere between November and April then you can get an influenza vaccination. You should get a vaccination for Japanese encephalitis in case you tour is for more than a month and you intend to visit the rural areas during June till September. Two doses for Measles, mumps, rubella (MMR) vaccinations are recommended if you are born after 1956 or you have not been previously vaccinated. It is also recommended that you get re-vaccinated for Tetanus and diphtheria if you have not been vaccinated for the past 10 years.