Safety and dose-sparing effect of Japanese encephalitis vaccine administered by microneedle patch in uninfected, healthy adults (MNA-J): a randomised, partly blinded, active-controlled, phase 1 trial.

Background: It is unclear whether microneedle vaccinations of Japanese encephalitis virus can induce sufficient neutralising antibodies and reduce the amount of vaccine needed. We aimed to assess the safety and dose-sparing effect of a microneedle vaccine patch against Japanese encephalitis in healthy individuals who are naive to both the vaccine and natural infection.

Methods: The MNA-J study was a randomised, partly blinded, active-controlled, phase 1 clinical trial at Hokkaido University (Sapporo, Japan) that enrolled healthy adults aged 20-34 years with no history of Japanese encephalitis vaccination nor of infection as confirmed by seronegativity. We excluded individuals who had been infected with or vaccinated against Japanese encephalitis. Eligible participants were randomly assigned (1:1:1) to one of three groups to receive inactivated Japanese encephalitis vaccine administered twice, 3 weeks apart, by either 2·5 μg per injection by subcutaneous injection, 0·63 μg per patch by high-dose microneedle array (MNA-25%), or 0·25 μg per patch by low-dose microneedle array (MNA-10%). The randomisation sequence, using stratification by cohort and blocks of six, was computer-generated by a statistician who was unaware of group assignment. After administration, the remaining amount of unadministered vaccine was measured by ELISA and calculated as the delivered amount of vaccine. The primary outcome was the neutralising antibody titre at day 42 after first immunisation. Successful seroconversion was defined as post-vaccination titres of 1·3 (log) or higher in individuals whose pre-vaccination titres had been less than 1 (log). This study is registered with the Japan Registry of Clinical Trials (s011190004).

Findings: Between Aug 31 and Sept 2, 2019, 39 participants were enrolled and each was randomly assigned to a group (n=13 per group). No serious adverse events were observed. All participants in the microneedle array groups had a localised erythematous reaction. The amount of vaccine delivered by microneedle array to each participant was 0·63-1·15 μg (50-92%) of the full 1·26 μg for the MNA-25% group and 0·25-0·41 μg (51-84%) of the full 0·50 μg for the MNA-10% group. All participants demonstrated seroconversion at day 42, and the mean titres (log) were 2·55 for MNA-25%, 2·04 for MNA-10%, and 2·08 for subcutaneous injection.

Interpretation: A microneedle patch of the Japanese encephalitis vaccine is safe, well tolerated, and immunogenically effective. The dose-sparing effect suggests a significant potential to reduce the amount of immunogens needed. However, improved delivery is needed to make it more tolerable and user friendly.

Funding: FUJIFILM.