Encephalitis vaccine
The encephalitis vaccine is designed to prevent Japanese encephalitis (JE), a viral infection that can lead to severe neurological complications and even death. Primarily found in Asia, JE is transmitted through infected mosquitoes, making vaccination particularly important for travelers to endemic regions. In the United States, two types of JE vaccines are available: JE-VAX, which was discontinued in 2006, and Ixiaro, a newer vaccine approved in 2009 that uses cell culture technology. Public health recommendations suggest vaccination for individuals traveling for a month or more to areas where JE is common, especially in rural settings or during outbreaks.
Ixiaro is administered in two doses, spaced 28 days apart, with the second dose ideally given at least one week prior to travel. While the vaccine has a very low risk of serious side effects, mild reactions such as headaches and soreness at the injection site may occur. The overall impact of JE vaccination is significant, with reductions in infection rates observed in countries like Thailand and Japan, underscoring the importance of immunization in preventing this serious disease.
Encephalitis vaccine
Also known as: Japanese encephalitis vaccine
Definition
The encephalitis vaccine is used to prevent infection with Japanese encephalitis (JE), which is caused by a virus that affects the brain and can sometimes result in death. The virus, found primarily in Asia, is transmitted through infected mosquitoes.
History and Development
There are two types of JE vaccine licensed for use in the United States, JE-VAX and Ixiaro. JE-VAX, derived from mouse brains, was licensed for use in adult and pediatric (age one year and older) travelers in 1992. However, production of JE-VAX was discontinued in 2006, and stockpiles are expected to be depleted shortly. Ixiaro, a second-generation vaccine approved in 2009, is manufactured using cell culture technology. Research in the United States and Europe showed that Ixiaro produced sufficient levels of antibodies to protect against JE.
Recommendations
The Centers for Disease Control and Prevention (CDC) recommends vaccination against JE for people traveling to Asia who will spend one month or more in areas where JE occurs, who plan to visit rural areas or engage in outdoor activities, who expect to travel in areas of JE outbreak, and who are unsure of their exact plans while travelling. Laboratory workers who may be exposed to the JE virus should also be vaccinated.
Pregnant women are advised to avoid the vaccine, as are persons with a history of a severe allergic reaction to a previous dose of the JE vaccine or any other vaccine or vaccine component. Travelers who plan to return from Asia within thirty days and who will stay in major urban areas should consult a doctor before travel, because in these cases, the vaccine may not be recommended.
Administration
Ixiaro is given to people seventeen years of age and older in two separate doses, twenty-eight days apart. The second dose should be given a minimum of one week before travel. The need for and timing of Ixiaro booster shots is not yet known.
Side Effects
The risk of Ixiaro causing serious harm or death is extremely small. Data on Ixiaro are limited thus far; severe reactions to Ixiaro are very rare, and other reported symptoms, including headache, muscle aches, pain, and tenderness, redness, or swelling at the injection site, are mild.
Impact
The impact of JE vaccination is expected to be significant, especially in countries where the disease is more prevalent. The vaccines will prevent illness, disability, and death. JE infection rates have fallen in Thailand and Japan as a result of vaccination.
Bibliography
Booss, John, Margaret Esiri, and Margaret M. Esin, eds. Viral Encephalitis in Humans. Washington, D.C.: ASM Press, 2003.
Centers for Disease Control and Prevention. “Japanese Encephalitis.” In CDC Health Information for International Travel 2010. Available at http://wwwnc.cdc.gov/travel/content/yellowbook/home-2010.aspx.
Plotkin, Stanley A., Walter A. Orenstein, and Paul A. Offit. Vaccines. 5th ed. Philadelphia: Saunders/Elsevier, 2008.
United Nations International Children’s Emergency Fund (UNICEF). “Vaccine Is Key to Preventing Outbreaks of Japanese Encephalitis.” Available at http://www.unicef.org/infobycountry/india‗28555.html.