A Phase 2 Double Blind Study to Evaluate Safety and Immunogenicity of Meningococcal Meningitis Serogroups A, C, Y & W-135 Polysaccharide Diphtheria Toxoid Conjugate Vaccine (NmVac4-A/C/Y/W-135-DT™) Compared With a Licensed Vaccine

Meningococcal disease is a potentially life-threatening bacterial infection. The disease most commonly is expressed as either meningococcal meningitis, an inflammation of the membranes surrounding the brain and spinal cord, or meningococcemia, the presence of bacteria in the blood. The most common symptoms include high fever, headache, neck stiffness, confusion, nausea, vomiting, lethargy, and rash. If not treated the disease can progress rapidly and can lead to shock and death, often within hours of the onset of symptoms. The disease is fatal at a rate of 10%. Of patients who recover, 10% have permanent hearing loss or other serious sequelae.

Neisseria meningitidis capsular polysaccharides are poor immunogens. However, conjugation of bacterial polysaccharides to immunogenic carrier proteins generally results in conjugates that induce strong anti-polysaccharide T-helper cell dependent immune responses, creating a longer-lasting immune response and thus protection against meningococcal infection.

The sponsor's small size Phase 1 clinical trial comprised 60 subjects. Therefore, additional data is needed to confirm the previous data with a statistically powered Phase 2 clinical trial. The present study aims to evaluate subject responses to single doses, administered in adult subjects, to determine further safety and immunogenicity of the vaccine. This study compares safety and antibody production induced by one intramuscular injection of either NmVac4-A/C/Y/W-135-DT or a licensed meningococcal (Groups A, C, Y, W-135) polysaccharide diphtheria toxoid conjugate vaccine. The primary immunogenicity endpoint will be seroresponse, based on antibody titer ≥1:8 for subjects with titer <1:8 at baseline or a 4-fold rise in antibody levels, 4 weeks after a single injection . The number and proportion of subjects achieving seroresponse will be tabulated by serogroup for each vaccine group. A non-inferiority test will be used to determine if the immune response elicited by NmVac4 A/C/Y/W-135-DT™ is not less than a specified difference in percent seroconversion from the licensed control vaccine. Participants will attend a screening visit up to 6 weeks prior to vaccination (day 0), then will attend study visits for 4 weeks. There will be a study phone call at days 2-3, then a post-study call to subjects to assess safety at 26 weeks.