A Phase 2 Randomized Multisite Trial to Inform Public Health Strategies Involving the Use of MVA-BN Vaccine for Mpox

Plain-language summary

This study is a Phase 2 open-label, non-placebo controlled, multi-site clinical trial that will evaluate the standard SC regimen in adolescents ages 12 through 17 years, inclusive, and compared to the standard subcutaneous regimen in adults ages 18 to 50, inclusive. Approximately 135 healthy, vaccinia-naïve adults will be enrolled in a comparator arm (Arm 4) and will be given the standard, licensed regimen of 1x10\^8 TCID50 MVA-BN administered SC on Day 1 and 29. These adults (Arm 4) will be combined with the 76 healthy, vaccinia-naïve adults that received the standard SC regimen in Stage 1 (Arm 3). Together, this will be the comparator group for non-inferiority testing for the primary endpoint. Approximately 315 healthy, vaccinia-naïve adolescents will be enrolled and given 1x10\^8 TCID50 MVA-BN administered SC on Days 1 and 29 (Arm 5). The study will have a set target enrollment of at least 25% adolescents ages 12 to 14 years, inclusive, to ensure that adequate numbers of younger adolescents are enrolled. The primary objectives are 1.) to determine if peak (Day 43) humoral immune responses in adolescents ages 12 to 17 years following administration of a 2-dose 1 x 10\^8 TCID50 MVA-BN regimen administered SC are non-inferior to the response in adults ages 18 to 50 years who received the licensed 2-dose SC regimen of 1 x 10\^8 TCID50 MVA-BN ; and 2.) to describe safety of a 2-dose 1 x 10\^8 TCID50 MVA-BN regimen administered SC in adolescents ages 12 to 17 years.

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