Introduction
  The number of Japanese overseas travelers decreased temporarily due to SARS, and it has been reported to reach 17 million annually (Figure 1).

The number of long term overseas residents has exceeded one million and foreign countries have become very close to a home country. Unlike Japan, however infectious diseases have not been brought under control in developing countries, and the risk of contracting an infection remains high. Travel medicine is developed in Western countries, and travelers clinics located in every city provide the necessary immunization with travelers vaccines before going abroad. There are travel clinics only in a few big cities in Japan. Since many travelers vaccines are vaccines against infectious diseases that have been brought under control in Japan, they have not been approved in this country. Immunization with vaccines that take time before becoming effective must originally be completed before leaving. However, many Japanese have numerous opportunities to be vaccinated overseas. It will be necessary in future to take some kind of measures so that the Japanese may also be vaccinated before traveling abroad, which is the primary purpose of vaccination. We are carrying out a "Study on the concept of overseas travelers" under a subsidy for scientific surveys from the Ministry of Health, Labour and Welfare. We are aiming at clarifying the current situation in Japan building up a system allowing travelers to receive travelers vaccines easily without undue worries.
  We will briefly explain in this article the vaccines necessary for long term residents in foreign countries, regardless these vaccines have been approved or not.
1. Vaccines required in industrialized countries
  Vaccination has two objectives. The first is to protect the individual, and the second is to protect the individual by controlling the outbreak through boosting the herd immunity. Vaccines for the protection of the individual traveler are needed when going to a developing country, and vaccines protecting the group and the individual are required upon entry into an industrialized country. Therefore, the vaccines necessary for travelers differ with developing countries and industrialized countries. In the US, the country the most advanced in terms of the vaccination strategy, the vaccines required for adults are those against tetanus and hepatitis A and B. Since the immunization schedule for the vaccines necessary for children is not the same in Japan and in the US, the Japanese must receive additionally the vaccines that are not commonly administered in Japan (Table 1). Due the strong awareness about group protection in the US, preventive vaccination is needed for travelers to live in the US,if they have not yet been vaccinated. Hepatitis B vaccine, chickenpox vaccine, mumps vaccine, pneumococcal conjugate vaccine, Haemophilus influenzae type b conjugate vaccine and meningococcal vaccine are given routinely, and all long term residents from abroad are requested to receive these vaccines. Since hepatitis B vaccine, chickenpox vaccine and mumps vaccine have been approved in Japan, they may have been inoculated before traveling, but pneumococcal vaccine, Haemophilus influenzae type b vaccine and meningococcal vaccine are given in the US, since they have not been approved in Japan.
2. Vaccines required when traveling to developing countries
  The vaccines required in developing countries are those intended to protect only the vaccine recipient. The risk of acquiring the infectious diseases that could be prevented by vaccination differ depending upon the travel destination. Some vaccines are indispensable for travelers depending upon the destination. Figure 2 shows the areas where the yellow fever vaccine is required. They are distributed in tropical areas in Asia and Africa.

  In case of the yellow fever vaccine, a vaccination certificate called "Yellow Card" is issued after receiving one shot of the vaccine, and it is valid for ten years. In Japan, this vaccine is available only in a total of 19 quarantine stations and their affiliated facilities. There are no vaccines other than the yellow fever vaccine which restrict the entry into or the departure from a country. Table 2 shows the recommended vaccines by travel destination. In general there are many kinds of vaccines recommended for developing countries and they are vaccines against hepatitis A and B, tetanus and rabies. Besides, the recommended vaccines also vary with the different travel destination, for instance urban areas or mountains and forests. Thus it will be necessary to draw up a detailed vaccination program integrating the information such as whether the destination is an industrialized country or a developing country, the season, the behavioral pattern, the length of stay, the situation of outbreaks in the area of destination, and so forth.