Key result
Single-dose live and two-dose inactivated JE vaccines beat controls, achieving similar ~40% seroconversion rates.
Why the study?
Outbreaks of Japanese encephalitis emerged among adults born before vaccine availability in northern China, motivating evidence to guide adult targeted immunization efforts.
Do live attenuated or inactivated Japanese Encephalitis vaccines improve seroconversion and seropositivity in adults aged 40-69 years?
RCT (n=628)
Open-label
Age-stratified sequential allocation
No
Do live attenuated or inactivated Japanese Encephalitis vaccines improve seroconversion and seropositivity in adults aged 40-69 years?
Absolute Event Rate: 39.87% vs 10.97%
p-value: p=<0.0001
Both live attenuated and inactivated Japanese Encephalitis vaccines demonstrated good immunogenicity, immune persistence, and safety in adults aged 40-69 years, supporting adult vaccination in emerging endemic areas.
Hypothesis-generating for adult JE vaccination in endemic areas; leaves open optimal schedules and real-world effectiveness.
Live attenuated and vero-cell-inactivated Japanese Encephalitis vaccines (LJEV, IJEV) have been in common use in young children in China since 1989 and 2004, associated with large reductions in Japanese encephalitis (JE) incidence. In 2013, northern China reported JE outbreaks among adults born before JE vaccine availability, a trend that worsened in 2017-2018. We conducted an open-label, randomized, controlled trial (ChiCTR2500103235) to assess the immunogenicity, immune persistence, and safety of three JE vaccine schedules in 40-69-year-olds to provide evidence for adult targeted JE immunization efforts. Outcomes were seroconversion proportions and seropositive prevalences; adverse events were monitored. The vaccines were immunogenic with no significant difference between vaccination groups. Seropositivity remained above 80% at one year post-vaccination. No serious adverse events occurred. All three schedules had good, persistent immunogenicity and favorable safety profiles in 40-69-year-old adults, providing evidence supporting vaccinating adults in response to the emergence of adult JE in northern China.
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Wu et al. (2025) conducted an RCT in Japanese encephalitis (n=628). Live attenuated (LJEV) or inactivated (IJEV) Japanese encephalitis vaccine vs. Unvaccinated control was evaluated on Seroconversion proportion of JE virus-neutralizing antibodies 29 days after completing the vaccination schedule (p=<0.0001). In adults aged 40-69 years, a single dose of live attenuated Japanese encephalitis vaccine or two doses of inactivated vaccine yielded similar seroconversion proportions of 38-40%, significantly higher than the 11% seen in unvaccinated controls.
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