Japanese encephalitis is a mosquito-borne disease that is mainly caused by a bite of a mosquito with a Japanese encephalitis virus. There is no specific treatment for Japanese encephalitis, and doctors generally provide supportive treatment to patients. According to the World Health Organization, Japanese meningitis mortality can be as high as 20-30% among infected people. About 30-50% of survivors who have suffered from Japanese encephalitis have sequelae of the nervous system. Children are at high risk, and about 75% of infected people are born to 14 years old.

There is a vaccine in Hong Kong that can prevent Japanese encephalitis. Although Japanese encephalitis is not common in Hong Kong, citizens who plan to travel to high-risk areas during the disease-promoting season, or to the suburbs and spend most of their outdoor or night activities may consider taking a preventive vaccine before travelling to these areas.

Injection schedule ─ 9 to 17 years old need to be given two needles, two needles separated by 12-24 months.