This is an exploratory trial to assess the safety, tolerability and immunogenicity of vaccination with a tetravalent dengue vaccine (TDV) in healthy adults delivered intradermally using the conventional needle/syringe or a needle-free PharmaJet® injector.

Two (2) intradermal injections of either vaccine or placebo will be administered to qualified participants (one in each arm) on Day 0 of the study. A subsequent injection will also be given on Day 90 with either vaccine or placebo (in one arm only).

Participants will be evaluated for safety and dengue neutralizing antibodies to all four serotypes. All participants will also be evaluated for injection site reactions and have blood drawn for viremia, neutralizing antibodies, cell-mediated immunity, and innate immunity.

Participants will be required to participate for approximately 10 months from recruitment and collection of data for primary outcomes (through Day 120) including the collection of additional samples for measurement of longer-term antibody titers (through Day 270).

This project has been funded in whole or in part with Federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN272201000034C.

Results

Changes in World Health Organization prequalification guidance for new vaccines concerning storage conditions favored the use of lyophilized preparations, and led to the early cessation of enrolment, but not before 67 subjects were enrolled in four treatment groups.

Sixty-five subjects completed the planned schedule. There were no safety signals or serious adverse events. All vaccination regimens elicited neutralizing antibodies. Titers of neutralizing antibodies against serotypes 1 and 2 were higher than those against serotypes 3 and 4. There were no consistent increases in responses with two doses given either concomitantly or 90 days apart.

Conclusions: Simultaneous injection of two LD-TDV doses was shown to have the potential to improve seroconversion rates to serotypes 1 and 2, and to increase serotype 2 antibody titers. A primary dose of LD-TDV administered by PharmaJet was shown to induce more rapid seroconversion to serotypes 1, 2, and 3 compared with administration by needle-syringe.