The Japanese encephalitis (JE) virus is one of the most preventable strain of its kind.
Formaldehyde-inactivated JE Virus (P3 strain) derived vaccine, was the first vaccine that was developed in China. The vaccine was derived from laboratory-infected suckling mouse brains. It was tested and successfully developed, and manufactured in 1968.
China started administrating the P3 inactivated JE vaccine in 1983. However, due to its low production capacity, it was restricted to certain small areas. Individuals were immunized with five doses of the vaccine, two at 12 months of age with an interval of a week, subsequently one dose each at ages 2, 6, and 10 years old. The inactivated P3 vaccine was used up till 1988. In 1988, the first live-attenuated vaccine based on the SA 14-14-2 strain was approved for use in China. Individuals were given two doses of the vaccine, at 8 months of age and then 2 years later. As compared to inactivated vaccines, the live-attenuated vaccine was cheaper to manufacture and administer. It required lesser doses and the immunization process was easier. Hence, the use of the live-attenuated JE vaccine progressively increased and ultimately replaced the P3 inactivated JE vaccine. Since 2008, only the live-attenuated vaccine were administered in China after it was included in the national Expanded Program of Immunization (EPI).
Even though the inactivated JE vaccine was first made available in 1968, the Chinese government could not afford to immunize every citizen. Hence, only those who could afford the vaccine, were immunized. Whereas, most of the Chinese people, particularly those living in rural areas, were unable to bear the costs of immunization. Thus, there were low immunization coverage, resulting in insignificant impact on JE pandemic between 1971 to 1972.
When China’s economy stabilizes, an improved JE vaccination program was executed. EPI was introduced, whereby, the government covered the full costs of the immunization. This has greatly improved the JE immunization coverage, and the risk of infection by JE virus in mainland China dropped dramatically.
JE has finally become an affordable vaccine-preventable disease. The prevalence of JE in mainland China, as well as some countries, such as Korea and Japan, has decreased to the extent of almost eradication by immunization programs. Therefore, JE vaccination are recommended to be included in their national health programs, in JE prevalent countries with public health infrastructure and financial resources.
There is no cure for the disease and vaccination offers the best protection against the virus.
JE vaccines in Singapore,
Number of doses: Two over a month. One six weeks before travel and the other, two weeks before travel.
Cost: About $600 for two injections.