Post-Marketing Surveillance of Adverse Events Following Vaccination with the Live-Attenuated Japanese Encephalitis Chimeric Virus Vaccine (Imojev(R)) in South Korea, 2015-2019

Introduction The live attenuated Japanese encephalitis chimeric virus vaccine (JE-CV; Imojev(R)) has been approved in South Korea for use in subjects aged >= 12 months since 2015. As part of the license agreement, a post-marketing surveillance study was undertaken to actively monitor the safety profile of JE-CV in the Korean population. Methods An observational, active safety surveillance study was conducted from 3 April 2015 through to 2 April 2019 at 12 centers in South Korea. Subjects aged >= 12 months who received a single dose of JE-CV (primary or booster) during a routine healthcare visit were recruited and followed up for solicited reactions (7 and 14 days for injection site and systemic reactions, respectively), non-serious unsolicited adverse events and serious adverse events within 42 days after vaccination. Results Overall, 810 subjects who received JE-CV were included in our analysis, the majority received the vaccine as a primary vaccination (94.9%; 769/810). There were 179 solicited reactions reported by 111 subjects; the majority of solicited reactions occurred within 0-3 days (80.4%; 144/179), were of 1-3 days' duration (79.3%; 142/179) and of grade 1 intensity (70.9%; 127/179). There were three grade 3 adverse reactions (irritability, pyrexia and malaise); all resolved within a few days. The incidence of solicited reactions were highest in those aged 12 to < 24 months (34.7% [52/150] subjects; 107 events) and 2 to < 10 years (17.8% [8/45] subjects; 14 events). All unsolicited adverse events (serious and non-serious) were unrelated to vaccination. There were no discontinuations due to adverse reactions/events. Conclusion JE-CV has a good safety profile under practice conditions in South Korea. No new safety issues were identified.