Japanese encephalitis is the leading cause of viral neurological disease and disability in Asia. The severity of sequelae, together with the volume of cases, make JE the most important cause of viral encephalitis in the world. Approximately 3 billion people-including 700 million children-live in Asian areas at risk for JE. JE most commonly infects children between the ages of 1 and 15 years, and can also infect adults in areas where the virus is newly introduced. More than 50,000 cases are reported annually and cause an estimated 10,000 to 15,000 deaths. This figure is believed to represent only a small proportion of the disease burden that actually exists.~An effective vaccine has existed since 1941, but has not reached the poorest countries in Asia. During the 60 years that the vaccine has been available, JE has infected an estimated 10.5 million children, resulting in more than 3 million deaths and more than 4 million children living with long-term disabilities. Control of this disease has been limited due to poor disease surveillance, a limited and unstable vaccine supply, lack of guidance and programmatic support for immunization, and limited advocacy.~A successful vaccine should be safe, efficacious, affordable, administered in a single dose, and easily incorporated into the routine Expanded Programmes on Immunization (EPI) programs. This study will help ensure the safety of SA 14-14-2 simultaneously administered with measles vaccine, paving the way for its use in routine EPI programs. If this candidate becomes widely available, it will drastically increase the feasibility of routine JE immunization in Asia, reducing the devastating death and disability caused by this disease. In addition to impacting low-income countries, the vaccine will allow countries that purchase vaccine-such as Thailand, Vietnam, Sri Lanka, and India-to recover health care dollars, improve their present programs, and address other unmet health care needs.
This study will determine whether it is safe and effective to administer Japanese encephalitis (JE) live attenuated SA 14-14-2 vaccine at the same time as measles vaccine. If it is found to be safe, it will pave the way for use in routine vaccination programs. The hypothesis is that children who receive JE live attenuated SA 14-14-2 vaccine and measles vaccine at the same time are protected against these diseases at the same level as those who receive the vaccines at different intervals.