This is a Phase 1b, randomized, double-blind, dose-escalating, age de-escalating, placebo-controlled study of 200 children, ages 6 months to 17 years. This clinical trial is designed to assess the safety, tolerability/reactogenicity, and immunogenicity of one and two doses of Sing2016 M2SR H3N2 influenza vaccine (manufactured by FluGen) administered intranasally in seven cohorts of children.~The first two groups to be vaccinated will be Cohorts 1 and 2. Cohort 1 consists of 45 children 9-17 years old. Thirty of them will receive one dose of the vaccine at a dose of 10^9 TCID50, and 15 will receive one dose of placebo. Cohort 2 comprises 45 children 2-8 years old. Thirty of them will receive one dose of the vaccine at a dose of 10^8 TCID50 and 15 will receive one dose of placebo. Sites will enroll participants into Cohorts 1 and 2 simultaneously. Once 25 or more participants in each of the first 2 cohorts (Cohorts 1 and 2) have completed Day 8, SRC will evaluate if any halting rules are met and if it is deemed safe enrollment in Cohort 3 may open. Cohort 2 must fully enroll before enrollment in Cohort 3 may begin.~Cohort 3 consists of 25 children 2-8 years old. 15 of them will receive one dose of vaccine at 10^9 TCID50 and 10 will receive one dose of placebo. Once 25 participants in Cohort 3 have completed Day 8 of follow-up, similar to Cohorts 1 and 2, the SRC will review to ensure no halting rules are met and if no rules are met, and the SRC determines it is safe to proceed, simultaneous enrollment into Cohorts 4 and 5 can begin. If any halting rules are met or any concerns are raised by the SRC, an external SMC may meet to discuss the data for recommendations on either progression or clinical trial modification before progression to the next cohort.~Cohort 4 consists of 25 children 2-8 years old; 15 of them will receive two doses of vaccine at 10^9 TCID50 and 10 will receive two doses of placebo, with a 28-day interval between the first and second doses. Cohort 5 will enroll 8 influenza naïve children (defined as children without receipt of influenza vaccine and without previous documented influenza infection) who are 6-23 mo who will be randomly assigned to receive two doses of 10^7 TCID50 Sing2016 M2SR (n=6) or two doses of placebo (n=2) with a 28-day interval between the first and second dose. Once all 25 participants in Cohort 4 and all 8 of Cohort 5 have completed Day 36 of follow-up, the SRC will conduct a safety assessment to begin enrollment in Cohort 6.~Cohorts 6 and 7 will also enroll 6- to 23-month-olds who are influenza-naïve. Cohort 6 will consist of 26 children. A lead-in group of 8 children will be randomly assigned to receive either two doses of 10^8 TCID50 of the Sing2016 M2SR (n=6) or two doses of placebo (n=2). Once the first 8 children have completed Day 8 (8 days after first dose), the SRC will review the safety and determine if Cohort 7 may open to enrollment. Cohort 7 enrollment will not begin until Cohort 6 is fully enrolled. Similar to other cohorts, the additional 18 children in Cohort 6 may continue to enroll during the SRC review.~Cohort 7 will be the final cohort. Twenty-six children will be randomly allocated to receive two doses of either 10^9 TCID50 Sing2016 M2SR (n=18) or placebo (n=8). This cohort does not have a lead-in group since data from such a group are not needed to allow the enrollment in a subsequent cohort. However, the study-wide and individual halting rules still apply.~The primary study objective is to assess the safety and tolerability of one and two administrations of the Sing2016 M2SR H3N2 influenza vaccine at 10^7, 10^8, or 10^9 TCID50 delivered intranasally to healthy participants, 6 months to 17 years of age. The secondary study objective is to assess the humoral immunogenicity (serum antibody and mucosal antibody responses) directed against homologous viral strains after one and two administrations of Sing2016 M2SR H3N2 influenza vaccine at 10^7, 10^8, or 10^9 TCID50 delivered intranasally to healthy participants, 6 months to 17 years of age
This is a Phase 1b, randomized, double-blind, dose-escalating, age de-escalating, placebo-controlled study of 200 children, ages 6 months to 17 years. This clinical trial is designed to assess the safety, tolerability/reactogenicity, and immunogenicity of one and two doses of Sing2016 M2SR H3N2 influenza vaccine (manufactured by FluGen) administered intranasally in seven cohorts of children.~The first two groups to be vaccinated will be Cohorts 1 and 2. Cohort 1 consists of 45 children 9-17 years old. Thirty of them will receive one dose of the vaccine at a dose of 10^9 TCID50, and 15 will receive one dose of placebo. Cohort 2 comprises 45 children 2-8 years old. Thirty of them will receive one dose of the vaccine at a dose of 10^8 TCID50 and 15 will receive one dose of placebo.~Cohort 3 consists of 25 children 2-8 years old. 15 of them will receive one dose of vaccine at 10^9 TCID50 and 10 will receive one dose of placebo. Once 25 participants in Cohort 3 have completed Day 8 of follow-up, similar to Cohorts 1 and 2, the SRC will review to ensure no halting rules are met and if no rules are met, and the SRC determines it is safe to proceed, simultaneous enrollment into Cohorts 4 and 5 can begin. If any halting rules are met or any concerns are raised by the SRC, an external SMC may meet to discuss the data for recommendations on either progression or clinical trial modification before progression to the next cohort.~Cohort 4 consists of 25 children 2-8 years old; 15 of them will receive two doses of vaccine at 10^9 TCID50 and 10 will receive two doses of placebo, with a 28-day interval between the first and second doses. Cohort 5 will enroll 8 influenza naïve children (defined as children without receipt of influenza vaccine and without previous documented influenza infection) who are 6-23 mo who will be randomly assigned to receive two doses of 10^7 TCID50 Sing2016 M2SR (n=6) or two doses of placebo (n=2) with a 28-day interval between the first and second dose. Once all 25 participants in Cohort 4 and all 8 of Cohort 5 have completed Day 36 of follow-up, the SRC will conduct a safety assessment to begin enrollment in Cohort 6.~Cohorts 6 and 7 will also enroll 6- to 23-month-olds who are influenza-naïve. Cohort 6 will consist of 26 children. A lead-in group of 8 children will be randomly assigned to receive either two doses of 10^8 TCID50 of the Sing2016 M2SR (n=6) or two doses of placebo (n=2). Once the first 8 children have completed Day 8 (8 days after first dose), the SRC will review the safety and determine if Cohort 7 may open to enrollment. Cohort 7 enrollment will not begin until Cohort 6 is fully enrolled. Similar to other cohorts, the additional 18 children in Cohort 6 may continue to enroll during the SRC review.~Cohort 7 will be the final cohort. Twenty-six children will be randomly allocated to receive two doses of either 10^9 TCID50 Sing2016 M2SR (n=18) or placebo (n=8). This cohort does not have a lead-in group since data from such a group are not needed to allow the enrollment in a subsequent cohort. However, the study-wide and individual halting rules still apply.~The primary study objective is to assess the safety and tolerability of one and two administrations of the Sing2016 M2SR H3N2 influenza vaccine at 10^7, 10^8, or 10^9 TCID50 delivered intranasally to healthy participants, 6 months to 17 years of age