Comparison of Seroconverison Rates to the Japanese Encepalitis Live and Killed Vaccines in Children

Abstract

Introduction and objectives: Until year 2009, the Japanese encephalitis (JE) killed vaccine was used in the National Immunization program, which was then substituted with the JE live vaccine. Therefore, we proceeded to compare the seroconversion rates of these vaccines in a large cohort of children. Method: 608 children, aged 5-16, registered at the Family Practice Centre of the University of Sri Jayewardenapura, were recruited following informed written consent from parents. JE Detect IgG ELISA (Inbios) was used for the detection of IgG antibodies in serum to determine the JE antibody status. Calculation of the JE was done according to the manufacturers' instructions and accordingly an ISR (immune status ratio) of > 5 was considered positive; an ISR of 2-5 equivocal and an ISR of < 2 negative. 51 (9%) children had only partially completed the killed vaccine schedule and therefore, were excluded from the analysis. Results: 565 (92.9%) children were vaccinated against JE. 311 (55%) children had been given the live vaccine and 204 (36 %) the killed vaccine. We found that children who had received the killed JE were significantly more likely (p<0.001) to have seroconverted when compared to the live JE vaccine. 73 (35.8%) of those who received the killed vaccine had seroconverted to JE and 55 (26.9%) had an equivocal response, where as only 52 (16.7%) of those who received the live vaccine .sezoconverted and only 58 (18.6%) had an equivocal response. Conclusion: Children are significantly more likely to seroconvert with the killed JE vaccine