A Phase 2 Clinical Trial of VLA1553 in Healthy Children Aged 1 to 11 Years

This is a multicenter, prospective, randomized, observer-blinded, three arm, phase 2 clinical trial evaluating the full dose formulation of VLA1553, half dose formulation of VLA1553 and control (Nimenrix, a tetravalent meningococcal vaccine - Men ACWY). At least 300 male and female healthy children aged 1 to 11 years will be enrolled and the overall distribution of participants will be 2:2:1 to the two VLA1553 dose groups (n=120 each) or control (Nimenrix) (n=60). As a safety precaution measure, the first 30 sentinel participants will be enrolled into the trial in an open-label fashion according to an age step down scheme. After sentinel analysis, participants will be enrolled in a blinded, randomized manner into three Trial Arms. Within each treatment arm participants will be stratified into three age strata: Stratum A: 7 to 11 years -children from their 7th birthday until the day before their 12th birthday. Stratum B: 3 to 6 years - children from their 3rd birthday until the day before their 7th birthday. Stratum C: 1 to 2 years - children from their 1st birthday until the day before their 3rd birthday. Age strata for the VLA1553 treatment arms are targeted to be equal in size, i.e., approximately 40 per age stratum.