Key result
Japanese encephalitis vaccination is linked to an ~3-fold higher reporting rate of urticaria in VAERS.
Why the study?
Japanese encephalitis requires effective prevention and ongoing vaccine safety monitoring, but comprehensive analysis of adverse events associated with Japanese encephalitis vaccines was lacking.
Observational (n=1,384)
A considerable proportion of Japanese encephalitis vaccine adverse event reports in VAERS were serious, with prominent allergic reactions and specific brand-related signals such as loss of consciousness and seizures for IXIARO.
Answers are grounded in this paper and cite their sources.
VAERS signals for allergic reactions to JE vaccine warrant monitoring; hypothesis-generating and should not yet change practice.
Objectives Japanese encephalitis is a severe mosquito-borne disease requiring effective prevention and ongoing vaccine safety monitoring. This study aimed to analyze the characteristics, severity, and reporting trends of adverse events associated with Japanese encephalitis vaccines (JEV) in the U. S. Vaccine Adverse Event Reporting System (VAERS). We also investigated the correlation between Google search trends and adverse event reporting. Methods Data were extracted from VAERS (1993–2025). Descriptive statistics, including demographics and temporal trends, were performed. Disproportionality analysis used the reporting odds ratio (ROR) with a 95% confidence interval (CI). Google Trends analysis covered 2004–2025 (worldwide, topic: “Japanese Encephalitis Vaccine”). Results A total of 1,384 reports (6,596 vaccine-event pairs) were retrieved. IXIARO accounted for 3,452 pairs, JE-VAX 1368, J-VAX 698, and “unspecific Brand” 1,078. Serious reports totaled 284 (20.5%), and fatal reports 11 (0.80%). The 18–29 years group comprised 39.52% ( n = 547) of reports, while the ≥60 years group constituted 3.4% ( n = 47), with no fatal outcomes reported in this demographic. Key disproportionality signals (RORs) included nausea ( n = 134, ROR = 1.32), dizziness ( n = 132, ROR = 1.33), pruritus ( n = 127, ROR = 2.33), and urticaria ( n = 122, ROR = 2.89). Noteworthy brand-specific signals: IXIARO (loss of consciousness n = 32, ROR = 2.88; seizure n = 17, ROR = 2.97), JE-VAX (encephalitis n = 5, ROR = 15.69; angioneurotic oedema n = 4, ROR = 68.17), and J-VAX (laryngospasm n = 11, ROR = 185.73). Google search volume showed strong temporal correlation with VAERS reports (2004–2025). Conclusion This study revealed the reporting patterns of JEV vaccine adverse events in the VAERS database, indicating that a considerable proportion of reports were serious events, and allergic reactions such as pruritus, rash, and urticaria were prominent. The observed overlap between spontaneous reporting and online search trends suggests public awareness and information dissemination influence reporting patterns. These findings underscore the need for continued JEV safety surveillance and further investigation.
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Liu et al. (2025) conducted an observational in Adverse events following Japanese encephalitis vaccination (n=1,384). Japanese encephalitis vaccines vs. All other vaccines in VAERS was evaluated on Urticaria reporting (ROR 2.89, 95% CI 2.42-3.46). Japanese encephalitis vaccines were associated with significant disproportionality signals for adverse events in the VAERS database, most notably allergic reactions such as urticaria (ROR 2.89).
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