Abstract
BackgroundThe 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. MethodsIn this open-label, single arm trial in the Colombo District of Sri Lanka, generally healthy children 2 and 5years 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 365days 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. ResultsOf 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. 28days 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 28days 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. ConclusionAdministration 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.
Highlights
Japanese encephalitis (JE) is a flavivirus that is transmitted primarily by Culex mosquitoes from South Asia to regions of the Western Pacific
Most children previously vaccinated with inactivated mouse brain-derived JE vaccine (IMBV) had seroprotective levels of neutralizing antibodies against JE virus (98% of 2-year-olds and 99% of 5-year-olds) (Table 2)
Despite high baseline antibody levels, geometric mean titers (GMTs) rose substantially 28 days post-vaccination and persisted near these levels up to 1 year post-vaccination; by age group, GMTs among 2-yearolds 28 days post-vaccination were 3175 and among 5-year-olds were 2776
Summary
Japanese encephalitis (JE) is a flavivirus that is transmitted primarily by Culex mosquitoes from South Asia to regions of the Western Pacific. In several countries in Asia, such as Sri Lanka, national immunization programs previously relied on inactivated mouse brain-derived vaccine (IMBV), given in multiple doses (in primary series and as booster doses). 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. 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 WHO-prequalified CD-JEV vaccine to combat this disease of public health importance
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