Adverse events following immunization with the live-attenuated recombinant Japanese encephalitis vaccine (IMOJEV®) in Taiwan, 2017–18

•Taiwan adopted the use of JE-CV in the national immunization program in May 2017.•Report rate of AEs following receipt of JE-CV was 2.8 per 100,000 doses distributed.•Serious AEs were reported at a rate of 0.37 per 100,000 doses distributed.•Our post-licensure surveillance study supports the favorable safety profile of JE-CV. Japanese encephalitis (JE) is a significant public health concern in the Asia-Pacific region, with a case-fatality rate of around 20% for those who develop encephalitis. Mouse-brain derived vaccines against JE have been used in the publicly funded national immunization program (NIP) in Taiwan since 1968. They were replaced with a live-attenuated recombinant vaccine (JE-CV, IMOJEV®) in May 2017. We assessed reports of adverse events (AE) following the introduction of JE-CV into the Taiwan NIP to characterize its post-licensure safety profile. AEs reported between 1 May 2017 and 31 December 2018 post vaccination with JE-CV were extracted from the National Adverse Drug Reactions (ADR) Reporting System, a passive surveillance system run by the Taiwan Food and Drug Administration. The report rates were calculated based on the number of doses distributed by the manufacturer during the assessment period. There were 51 AEs reported among 30 subjects (12 girls and 18 boys; mean age 25 months), with a reporting rate of 4.7 AEs per 100,000 doses distributed. The AEs occurred after a median of. 1-day post vaccination. Eight subjects had received concomitant vaccination with another vaccines. There were four serious AEs reported: febrile seizure, acute renal failure, viral respiratory tract infection, and injection site cellulitis. None of these serious AEs were classified as being causally related to JE-CV vaccination. These post-licensure AE surveillance data confirm the favorable safety profile of JE-CV.