Immunizing Children Aged 9 to 15 Months with Live Attenuated SA14-14-2 Japanese Encephalitis Vaccine in Thailand
Tawee Chotpitayasunondh MD*, Young Mo Sohn MD**, Sutee Yoksan MD***, J. Min MSc****, Heechoul Ohrr MD*****
Affiliation : * Queen Sirikit National Institute of Child Health, College of Medicine, Rangsit University, Bangkok, Thailand ** Department of Pediatrics, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea, *** Japanese Encephalitis/Dengue Virology Laboratory, Center for Vaccine Development, Mahidol University, Bangkok, Thailand **** Glovax Ltd, Seoul, Korea ***** Department of Preventive Medicine, College of Medicine Institute for Health Promotion, Graduate School of Public Health, Yonsei University, Seoul, Korea
The authors aimed to evaluate the safety and immunogenicity of a live attenuated SA14-14-2 Japanese Encephalitis (JE) vaccine in healthy Thai infants. One hundred and fifty subjects aged 9-15 months were vaccinated with one dose of this vaccine. Regarding the vaccine safety, during the 28-day post-vaccination follow-up, no vaccine-related serious adverse events were reported. In terms of immunogenicity, the sero-conversion rate of a single dose vaccination was 95% (95% CI, 90.0-97.6%) within 90 days after vaccination and the geometric mean titer (GMT) was 66.1. Eight subjects with JE sero- negative on days 28-35 post-vaccination became sero-positive on day 90. Seven subjects who remained sero-negative during days 28-35 and day 90 post-vaccination were successfully sero-converted after receiving a second dose 3 months later. Thus, two doses of this JE vaccine resulted in a 100% (95% CI, 97.3-100%) sero-conversion rate with the GMT of 260.8. Eight children with GMTs lower than protective level after a single vaccination demonstrated a booster response with GMT of 1237 after the second dose of JE vaccination. In conclusion, the live attenuated SA14-14-2 vaccine was safe, well tolerated and highly immunogenic with 95% and 100% sero-conversion rate after one and two doses, respectively. Nevertheless, its long-term immune response and possible influences from natural dengue infection requires further evaluation.
Keywords : Japanese encephalitis, Vaccine, Immunogenicity
