Immunogenicity and protective effectiveness of japanese encephalitis vaccine: A prospective multicenter cohort study

Purpose: This study aimed to study the antibody response of Japanese encephalitis vaccination in children using different kinds of vaccines (inactivated vaccine, live attenuated vaccine or interchanged) and evaluate the effectiveness of the vaccines to provide the basis of efficient immunization schedule of Japanese encephalitis. Methods: Measurement of the neutralization antibody (NTAb) titers following Japanese encephalitis vaccination using different vaccines for 170 children, 2-6 year of age, who visited six university hospitals and are confirmed by immunization records. Results: Among 170 children who were given primary immunization on Japanese encephalitis, 103 children were given inactivated vaccine, 64 children were given live attenuated vaccine and 3 children were given interchangeably. NTAb titers were more than 1:10 in all children of three groups. The geographic mean antibody titer was 322 in inactivated vaccine group and 266 in live attenuated vaccine group. However, there was no significant difference between two groups. In both groups, the NTAb titer showed the peak at 1-4 months after the third immunization and declined. The NTAb titers of three children who were given two kinds of vaccines alternately were 1:135, 1:632, and 1:2511, respectively. Conclusion: According to the results of this study in children younger than 6 years old, there is no significant difference in effectiveness between inactivated and live attenuated vaccines. However, further studies for the changes of antibody titers for a longer period of time on larger population are required.