ATLANTA – Vaccination against Japanese encephalitis should be recommended for children aged 2 months to 16 years as a travel vaccine in certain situations, according to the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.
In a unanimous 13-0 vote, the committee supported the proposed recommendation of ACIP’s Japanese encephalitis (JE) vaccine workgroup to extend the current ACIP recommendation for JE vaccine in adults aged 17 years and older to children aged 2 months to 16 years, targeting people traveling at increased risk, based on their itineraries and activities. Until May, no vaccine for JE was available for children in the United States.
The 2009 recommendation for the JE vaccine in adults states the following:
• The JE vaccine is recommended for travelers who plan to spend 1 month or more in a JE-endemic area during the JE virus transmission season.
• The vaccine "should be considered" for short-term travelers (under 1 month) to endemic areas, if they are planning to travel outside of urban areas and have an increased risk of exposure to the JE virus (such as spending a "substantial time outdoors in rural or agricultural areas," or "participating in extensive outdoor activities").
• The vaccine also should be considered for travelers to an area with an ongoing JE outbreak, and travelers to endemic areas "who are uncertain of specific destinations, activities, or duration of travel."
• The vaccine is not recommended for short-term travelers who will be staying in urban areas only, or at times that are "outside of a well-defined JE virus transmission season."
The JE virus, a mosquito-borne flavivirus closely related to dengue and West Nile viruses, is endemic in China, Japan, and other parts of Asia, with the highest risk of in rural, agricultural areas.
Although the risk for most travelers to Asia is low, that risk varies depending on the destination, the duration and season of the visit, and activities, according to Dr. Marc Fischer of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), a member of ACIP’s JE vaccine workgroup. No cases of JE have been reported for travelers who only visited urban areas for short periods.
But JE is a severe disease with substantial morbidity and mortality, with no specific treatment available, and "the work group placed a high value on preventing this life-threatening disease," he said. Another consideration was the availability of a safe and effective vaccine, which provides high levels of seroprotection in children after 2 doses.
The vaccine that is available for adults – an inactivated cell culture derived JE vaccine (JE-VC) licensed by the Food and Drug Administration for adults aged 17 years and older – was also licensed for use in children aged 2 months to 16 years in May 2013. The vaccine is marketed as Ixiaro by Intercell Biomed, a Scottish company, and is distributed in the United States by Novartis. It is indicated for active immunization to prevent disease caused by JE virus and is administered as a two-dose primary series, 28 days apart.
The previously available JE vaccine, an inactivated mouse brain–derived JE vaccine, manufactured in Japan and licensed in the United States for people aged 1 year and older in 1992, is no longer available.
Between 1973 and 2012, there were 65 cases of travel-associated JE cases in the United States reported to the CDC or in the literature, including 6 (9%) of cases in children under age 17 years. Of the 65 cases, 13 (20%) were fatal, and of those who survived, 28 (43% of the total cases) had sequelae, Dr. Fisher said. Thailand was the "probable country of acquisition in most (32%) of these cases, followed by China (14%) Indonesia (14%), the Philippines (11%), Japan (6%) and Vietnam (5%), he said. In the remaining 18%, the probable country of acquisition was unknown.
Although the vaccine is expensive (about $200 a dose) and the risk of JE is not high, Dr. Fisher cited U.S. survey data indicating that parents would be willing to pay a high price for a vaccine to prevent a serious outcome.
Several members of the panel observed that the JE-VC vaccine is not likely to be provided in most general clinical practices, and that it would more likely be found in a travel medicine clinic. Cost was another issue cited, because travel vaccines are usually not covered by medical insurers.
There are 15 members in immunization-related fields on ACIP, which develops written recommendations for the routine administration of vaccines to children and adults in the civilian population; 13 members were present at this meeting.