This is very diverse region indeed and ranges from PRC (China) to Japan, Mongolia, Vietnam, Korea etc

Japan

Vaccines: Your health care provider may offer you vaccination against hepatitis B, influenza, Japanese encephalitis, tick-borne encephalitis, or typhoid.

There is no Malaria

Sanitation is generally good, and health concerns related to foods and beverages are minimal.

There is a risk of trematode infection (liver, lung, and intestinal worms) from eating undercooked fish and shellfish, and raw vegetables and salads.

Diseases transmitted by insects are not generally a problem in this country, although mosquitoes transmit Japanese encephalitis and ticks transmit tick-borne encephalitis and Lyme disease.

China and Other Regions of the Far East

A yellow fever vaccination certificate is required for travelers coming from areas with risk of yellow fever transmission.
Your health care provider may offer you vaccination against hepatitis A, hepatitis B, influenza, Japanese encephalitis, rabies, or typhoid. Routine immunizations, such as those that prevent tetanus/diphtheria or "childhood" diseases, should be reviewed and updated as needed.

A risk (P. falciparum) exists in many rural areas of the Far East, including China, Vietnam Laos, and Burma. Where there is transmission, it generally occurs below 1,500 meters from May to November.

Please visit: http://www.who.int/countries/en/ for specific country information.