Furuya-Kanamori L, Gyawali N, Mills Mbbs Mphtm DJ, Mills C, Hugo LE, Devine GJ, Lau CL. Immunogenicity of a single fractional intradermal dose of Japanese encephalitis live attenuated chimeric vaccine.
J Travel Med 2022;
30:6779982. [PMID:
36308439 DOI:
10.1093/jtm/taac122]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/09/2022] [Accepted: 10/14/2022] [Indexed: 11/14/2022]
Abstract
BACKGROUND
Japanese encephalitis (JE) is endemic in Asia and the western Pacific. Vaccination is recommended for travellers to endemic regions, but the high cost of the vaccine is a major barrier to uptake.
METHODS
A quasi-experimental, pre-post intervention clinical trial without a control group was conducted to assess the immunogenicity and safety of intradermal (ID) JE vaccine. Healthy adults (18-45 years) received one dose of 0.1 mL (20% of standard dose) ID Imojev® (JE live attenuated chimeric vaccine, Sanofi-Aventis). Adverse events following immunisation (AEFIs) were recorded 10 days post-vaccination. Blood samples were collected at baseline, 4, and 8 weeks post-vaccination. Neutralising antibodies were measured using 50% plaque reduction neutralisation test (PRNT50). Seroconversion was defined as PRNT50 titre ≥10. An in vitro study was also conducted to quantify the rate of decay of vaccine potency after reconstitution.
RESULTS
51 participants (72.6% females, median age 31 years), all non-reactive to JE virus at baseline were enrolled. Mild and moderate AEFIs were reported by 19.6% of participants; none required medical attention or interfered with normal daily activities. All participants seroconverted at 4 weeks (GMT 249.3; 95%CI:192.8-322.5) and remained seropositive at 8-weeks (GMT 135.5; 95%CI:104.5-175.6). Vaccine potency declined at a rate of 0.14 log plaque-forming units/0.5 mL per hour.
CONCLUSIONS
In healthy adults, a single 0.1 mL ID dose of Imojev was safe and immunogenic, at least in the short-term. Reconstituted vials of Imojev vaccine may not retain their potency after 6 hours. Fractional JE ID vaccination could be a cheaper yet effective alternative for short-term travellers. Further studies need to investigate the immune response in a wider age range of individuals and the long-term immunogenicity of fractional JE ID vaccines.
CLINICAL TRIALS REGISTRATION
ACTRN12621000024842.
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