Q: I took an immunisation for Japanese Encephalitis 3 years ago. Do i need to take it again. Please note, my job requires me to travel to China, and other South East Asian countries. Please advise.

A:The period of protection depends upon the exact type of vaccine, but like all viral vaccines it is very long. One strain is the vaccine manufactured in Japan (Nakajima). In this vaccine, when properly administered (2 doses plus booster), we generally advise children below 15 years to take a booster every 5 years. After the age of 15 years, the disease is very uncommon and therefore we are generally satisfied with assuming a longer period of protection. In your case you can safely assume that you do not need re-immunisation yet, but for a more specific answer details of the vaccine strain and immunisation procedure would be required. In any case, immunised or not, when you go to an area endemic for Japanese Encephalitis, personal precautions should be taken to avoid mosquito bites.