Safety of a live-attenuated Japanese encephalitis virus vaccine (SA14-14-2) for children

In a study begun in 1985, 1,026 children between the ages of 5 and 12 years, living in an area of low Japanese encephalitis (JE) infection, were vaccinated with live-attenuated JE vaccine, strain SA14-14-2. A group of 47 of the vaccinated children, 5-6 years of age, were examined for fever and other systemic reactions every other day for 2 weeks following vaccination. None of these children had temperatures greater than 37.4 degrees C or other systemic reactions during the observation period. No untoward reactions were reported in the remainder of the vaccinated group. After immunization, seroconversion rates in seronegative children were 100% (GMT 35.3, n = 11), 100% (GMT 31.7, n = 12), and 83.3% (GMT 23, n = 10) in groups receiving vaccine diluted 1:3, 1:5, and 1:50, respectively. These results indicate that the JE SA14-14-2 live-attenuated vaccine is immunogenic and safe for children.