Pushpa Ranjan WijesingheM. R.Nihal AbeysingheSutee YoksanYafu YaoBenli ZhouLei ZhangJessica A. FlemingAnthony A. MarfinJohn C. VictorMinistry of Health ColomboMahidol UniversityChengdu Institute of Biological ProductsPATH Seattle2018-12-112019-03-142018-12-112019-03-142016-11-21Vaccine. Vol.34, No.48 (2016), 5923-5928187325180264410X2-s2.0-84994652636https://repository.li.mahidol.ac.th/handle/20.500.14594/42248© 2016 The Author(s) Background The performance of live attenuated Japanese Encephalitis SA 14-14-2 vaccine (CD-JEV) among children previously given inactivated mouse brain-derived JE vaccine (IMBV) is unknown. We evaluated the safety and immunogenicity of CD-JEV administered to 2- and 5-year-old children in Sri Lanka. Methods In this open-label, single arm trial in the Colombo District of Sri Lanka, generally healthy children 2 and 5 years of age who had previously received two and three doses of IMBV, respectively, were administered one dose of CD-JEV subcutaneously. Participants were monitored for adverse events for one year post-vaccination. Serum neutralizing antibody responses were evaluated pre and 28 and 365 days post-vaccination using JE plaque reduction neutralization test and characterized as the proportion of participants seroconverting. Seroconversion was defined as either reaching a titer considered seroprotective (⩾1:10) among participants with a baseline titer <1:10 or achieving at least a 4-fold rise in titer among participants with a baseline titer ⩾1:10. Results Of 305 children given CD-JEV, 294 were included in the primary analysis of immunogenicity. Prior to vaccination, 144/147 (98.0%) 2-year-olds and 146/147 (99.3%) 5-year-olds had seroprotective levels. 28 days post-vaccination, 79/147 [53.7% (95% CI, 45.3–62.0)] 2-year olds and of 60/147 [40.8% (95% CI, 32.8–49.2)] 5-year olds achieved seroconversion. Among 2-year-olds, geometric mean titers (GMTs) rose from 697 to 3175 28 days post-vaccination. Among 5-year-olds, GMTs rose from 926 to 2776. Most adverse reactions were mild, and no serious adverse events were related to study vaccination. Conclusion Administration of CD-JEV to these children with pre-existing neutralizing JE antibody titers was safe and resulted in substantial boosting of antibody levels. These results may inform other countries in Asia considering switching from IMBV to now WHO-prequalified CD-JEV vaccine to combat this disease of public health importance.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyImmunology and MicrobiologyMedicineArticleSCOPUS10.1016/j.vaccine.2016.10.028