Children aged 2 months through 16 years should be vaccinated against Japanese encephalitis (JE) if they are going to be traveling to areas that are endemic for the disease.
A panel of 15 immunization experts convened by the Centers for Disease Control and Prevention (CDC), in Atlanta, voted unanimously to add the younger age group to the existing recommendations for travelers aged 17 years or older, which were made in 2009.
The request to add young children to the recommendations was put before the CDC's Advisory Committee on Immunization Practices (ACIP) by Marc Fischer, MD, medical epidemiologist with the CDC’s Arboviral Diseases Branch in Fort Collins, Colorado.
Fatal Disease With No Treatment
Japanese encephalitis is endemic to Asia and the Western Pacific and is transmitted by mosquitoes.
"There is no treatment for Japanese encephalitis and it is fatal in 20 to 30 percent of people who get the infection, and about a third to a half of the survivors have some neurologic, cognitive or behavioural sequelae," Dr. Fischer told Medscape Medical News.
He presented data to the ACIP panel that demonstrated that the JE vaccine, which was licensed for use in children aged 2 months or older in May of this year, is safe and effective.
The vaccine is marketed by Novartis as IXIARO.
"This is a safe vaccine, it has a low incidence of serious adverse events and in the studies that we reviewed, which included 3 in children and 9 in adults, the serious adverse events were similar to those seen in Prevnar and Havrix, the comparison vaccines," Dr. Fischer said.
In the period between 1973 and 2012, there have been 65 cases (59 adults, 6 children) of JE among US travelers.
Eleven (19%) adults and 2 (33%) children died, 25 (42%) adults and 3 (50%) children survived with sequelae, and 15 (25%) adults and zero children had no sequelae. Details of the remaining 8 adults and 1 child are unknown, Dr. Fischer said.
Itineraries for 47 of the travel-associated cases revealed that the majority (30, or 64%) had a travel duration of 1 month or more, 13 (27%) traveled for 2 to 4 weeks, and 4 (9%) traveled for 1 to 2 weeks.
There were no cases of JE reported in short-term travelers visiting urban areas only. However, travel to rural areas was dangerous, with 17 individuals getting infected.
Relative Risk Is Low
The JE disease risk for most travelers is very low and varies on location, duration of travel, the season, and travel activities, Dr. Fischer said.
In addition, the vaccine, although safe and effective, is very expensive.
"These are all factors to be taken into account when making recommendations for who gets vaccinated," he said.
Vaccinating children living in endemic areas is cost-saving, but the JE vaccine for all travelers to Asia would not be cost effective, he said.
"Over 5 and a half million Americans travel to Asia each year, and the overall risk of Japanese encephalitis is low, less than 1 case per million travelers. Also, the cost of the vaccine is high, at $200 to $250 a dose. For some travelers, even a low risk of serious adverse events due to the vaccine may be higher than the risk for disease. Because of these factors, we think the JE vaccine should be targeted to travelers who are at increased risk for disease based on their planned itinerary," Dr. Fischer said.
Including Kids the Only Change
The current recommendations for vaccination stand, with the only addition the inclusion of children aged over 2 months.
As confirmed by the ACIP panel, these are as follows:
- The JE vaccine is recommended for travelers who plan to spend a month or longer in endemic areas during the JE virus transmission season. This includes long-term travelers, recurrent travelers, or expatriates who will be based in urban areas but are likely to visit endemic rural or agricultural areas during a high-risk period of JE virus transmission (Recommendation category A)
- The JE vaccine should be considered for short-term (less than1 month) travelers to endemic areas during the JE virus transmission season if they plan to travel outside of an urban area and have an increased risk for JE virus exposure (eg, spending substantial time outdoors in rural or agricultural areas, participating in extensive outdoor activities, staying in accommodations without air conditioning, screens, or bed nets). The JE vaccine should also be considered for travelers to an area with an ongoing JE outbreak and those traveling to endemic areas who are uncertain of specific destinations, activities, or duration of travel (Recommendation category B).
- The JE vaccine is not recommended for short-term travelers whose visit will be restricted to urban areas or times outside of a well-defined JE virus transmission season (Recommendation Category A).
Dr. Fischer has disclosed no relevant financial relationships.
CDC's Advisory Committee on Immunization Practices Meeting: June 19, 2013.