Travelers Often Fail to Receive Vaccine for Japanese Encephalitis

Emma Hitt, PhD

March 19, 2008

March 19, 2008 (Atlanta) — Among travelers with itineraries that put them at risk for the Japanese encephalitis (JE) virus, only 11% received the vaccine, according to new survey results.

The findings were reported here today by researchers from the Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, at the International Conference on Emerging Infectious Diseases 2008.

According to the CDC, JE transmission occurs principally in rural agricultural locations where flooding irrigation is practiced, but in many areas of Asia, these conditions may occur near, or occasionally within, urban centers. Of the 35,000 to 50,000 cases of JE reported to the World Health Organization each year, up to 15,000 deaths occur, and neurologic sequelae can be present in up to 50% of survivors.

To investigate compliance with the CDC's Advisory Committee on Immunization Practices (ACIP) recommendations for JE, Mark Duffy, DVM, a medical epidemiologist with the CDC's Division of Vector-Borne Infectious Diseases (DVBID), Fort Collins, Colorado, and colleagues surveyed US residents older than 18 years departing on 39 flights traveling to JE endemic countries.

Of 2590 travelers contacted, 67% responded. Of those responders, 62% indicated that they had sought medical advice from 1 or more sources before travel, and about one fourth were considered "at risk," defined as having plans to spend at least 30 days in Asia or more than 40% of their time in rural areas.

Of the at-risk travellers, 11% reported receiving the vaccine. In addition, although 44% of at-risk travellers visited a healthcare provider in anticipation of their trip, half stated that their healthcare provider had not offered or recommended the vaccine to them.

These findings indicate that there is "both a need and an opportunity to better educate travelers and healthcare providers regarding the ACIP recommendations for the use of JE vaccine," Marc Fischer, MD, MPH, a medical epidemiologist and study author with the DVBID, told Medscape Infectious Diseases.

Dr. Fischer noted that the only JE vaccine licensed for use in the United States is no longer being produced. "Sanofi Pasteur estimates that available supplies of the currently licensed JE vaccine may be exhausted as early as mid-2008. A new JE vaccine has been submitted for licensure in the United States and may be available for use in adult travelers within the next year," he said.

According to Dr. Fischer, the risk of JE for most travelers to Asia is very low but varies on the basis of season, destination, duration, and activities. "Clinicians should evaluate the risks of JE for their patients who will be traveling to Asia and should educate their patients regarding these risks," he said.

"The risk of acquiring JE is very different in different countries," noted Ernest A. Gould, PhD, former director of the Centre for Ecology and Hydrology, Oxford, England, and flavivirus expert. "Therefore, doctors may be confused when they read the recommendations which will not necessarily be identical for different parts of Asia," he told Medscape Infectious Diseases. "The clinician must be familiar with the different risks for the different diseases and also be able to deliver the rationale to the individual seeking advice, in a simple but informative manner."

He added, "It's important to keep in mind that there is a risk, even if it is small, and JE is not a trivial disease if it occurs in travellers from the Western Hemisphere."

More information on JE for healthcare providers is available on the CDC's Web site at http://wwwn.cdc.gov/travel/yellowBookCh4-JapaneseEncephalitis.aspx.

The study was conducted and funded by the CDC's National Center for Zoonotic, Vector-Borne, and Enteric Diseases.The authors and commentator have disclosed no relevant financial relationships.

International Conference on Emerging Infectious Diseases 2008: Slide Session O2. Presented March 19, 2008.

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