Vaccine Information: FLUCELVAX QUADRIVALENT (PRE-FILLED SYRINGE) (Page 4 of 5)

14.4 Immunogenicity in Children and Adolescents 6 months through 17 years of age

Immunogenicity of FLUCELVAX QUADRIVALENT was evaluated in two clinical studies in children 6 months through 3 years of age (Study 1) and 4 through 17 years of age (Study 5).

Study 1 was a randomized, observer-blind, multicenter study in children 6 months through 3 years of age conducted in the US. In this study, subjects received FLUCELVAX QUADRIVALENT or a US-licensed comparator quadrivalent influenza vaccine (FLUCELVAX QUADRIVALENT N=1597, Comparator QUADRIVALENT (QIV) N=805). In the per protocol set, the mean age of subjects who received FLUCELVAX QUADRIVALENT was 29 months; 49% of subjects were female and 67% of subjects were Caucasian, 27% were Black and <1% were Asian, Hawaiian or other Pacific Islander and American Indian or Alaska Native. Twenty six percent of subjects were of Hispanic origin. The immune response to each of the vaccine antigens was assessed 28 days after last vaccination.

The immunogenicity endpoints were geometric mean antibody titers (GMTs) and percentage of subjects who achieved seroconversion, defined as a pre-vaccination HI or microneutralization (MN) titer of <1:10 with a post-vaccination titer ≥1:40 or with a pre-vaccination HI or MN titer ≥ 1:10 and a minimum 4-fold increase in serum antibody titer. GMTs and seroconversion rates were measured by hemagglutination inhibition (HI) assay for A/H1N1, B/Yamagata and B/Victoria strains and by microneutralization (MN) assay for the A/H3N2 strain.

FLUCELVAX QUADRIVALENT was noninferior to the Comparator QIV. Noninferiority was established for all 4 influenza strains as assessed by ratios of GMTs and the differences in the percentages of subjects achieving seroconversion at 4 weeks following vaccination.

The noninferiority data observed are summarized in Table 9.

Table 9: Noninferiority 1 of FLUCELVAX QUADRIVALENT Relative to Comparator QIV in Children 6 Months through 3 Years of Age – Per-Protocol Analysis Set 2 (Study 1)

Abbreviations: GMT = geometric mean titer. CI = confidence interval.

Assays: GMTs and seroconversion rates were measured by hemagglutination inhibition (HI)* assay for A/H1N1, B/Yamagata and B/Victoria strains and by microneutralization (MN)# assay for the A/H3N2 strain, using cell-derived target viruses. The MN assay was used for A/H3N2 as circulating strains indicated a reduced ability to agglutinate red blood cells. FLUCELVAX QUADRIVALENT was noninferior to the Comparator QIV irrespective of the assay used. HI assay data for A/H3N2: GMT (95%CI) for FLUCELVAX QUADRIVALENT (N=1089) = 288.1 (261.46, 317.54), Comparator QIV (N=575) = 227.6 (201.87, 256.58), Vaccine group ratio (95%CI) = 0.79 (0.69, 0.90), Seroconversion rate (95%CI) for FLUCELVAX QUADRIVALENT (N=1089) = 72.27% (69.51,74.91), Comparator QIV (N=575) = 64.52% (60.46, 68.44), Vaccine Group Difference (95%CI) = -7.75% (-12.51, -3.06).

Success criteria: The upper bound of the two-sided 95% confidence interval (CI) on the ratio of the GMTs (calculated as GMT US-licensed comparator QIV divided by GMT FLUCELVAX QUADRIVALENT) does not exceed 1.5. The upper bound of the two-sided 95% CI on the difference between the seroconversion rates (calculated as Seroconversion rate US-licensed comparator QIV minus Seroconversion rate FLUCELVAX QUADRIVALENT) does not exceed 10%.

1 Analyses are performed on data for Day 29 for previously vaccinated subjects and Day 57 for not previously vaccinated subjects

2 Per protocol set: All participants in Full Analysis Set, immunogenicity population, who have correctly received the assigned vaccine, have no major protocol deviations leading to exclusion as defined prior to unblinding/ analysis and are not excluded due to other reasons defined prior to unblinding or analysis.

3 Seroconversion rate = percentage of subjects with either a pre-vaccination titer <1:10 and post-vaccination titer ≥1:40 or with a pre-vaccination titer ≥1:10 and a minimum 4-fold increase in post-vaccination antibody titer

Study 1: NCT 04074928

FLUCELVAX QUADRIVALENT Comparator QIV Vaccine Group Ratio Vaccine Group Difference
A/H1N1* N = 1092 N =575
GMT (95% CI) 78.0(70.75, 86.03) 57.3(50.76, 64.63) 0.73(0.65, 0.84)
Seroconversion Rate 3 (95% CI) 58.24%(55.25, 61.19) 46.78%(42.64, 50.96) -11.46(-16.45, -6.42)
A/H3N2# N = 1078 N = 572
GMT (95% CI) 23.1(21.21, 25.12) 23.9(21.57, 26.57) 1.04(0.93, 1.16)
Seroconversion Rate 3 (95% CI) 27.64%(24.99, 30.42) 30.77%(27.01, 34.73) 3.13(-1.44, 7.81)
B/Yamagata* N = 1092 N = 575
GMT (95% CI) 35.6(32.93, 38.58) 26.0(23.54, 28.63) 0.73(0.66, 0.81)
Seroconversion Rate 3 (95% CI) 46.52%(43.53, 49.53) 31.65%(27.87, 35.63) -14.87(-19.61, -9.98)
B/Victoria* N = 1092 N = 575
GMT (95% CI) 22.4(20.70, 24.19) 19.6(17.81, 21.58) 0.88(0.79, 0.97)
Seroconversion Rate 3 (95% CI) 30.31%(27.60, 33.13) 24.35%(20.89, 28.07) -5.96(-10.33, -1.44)

Study 5 was a randomized, double-blind, controlled study in children and adolescents 4 through 17 years of age conducted in the US. In this study, 1159 children and adolescents received FLUCELVAX QUADRIVALENT. In the per protocol set, the mean age of children and adolescents who received FLUCELVAX QUADRIVALENT was 9.8 years; 47% of children and adolescents were female and 54% of children and adolescents were Caucasian, 22% were black and 19% were Hispanics. The immune response to each of the vaccine antigens was assessed, 21 days after vaccination.

The immunogenicity endpoints were the percentage of children and adolescents who achieved seroconversion, defined as a pre-vaccination hemagglutination inhibition (HI) titer of < 1:10 with a post-vaccination HI titer ≥ 1:40 or at least a 4-fold increase in serum HI titer; and percentage of children and adolescents with a post-vaccination HI titer ≥ 1:40.

In children and adolescents receiving FLUCELVAX QUADRIVALENT, for all four influenza strains, the 95% LBCI seroconversion rates were ≥ 40% and the percentage of children and adolescents who achieved HI titer ≥1:40 post vaccination were ≥ 70% (95% LBCI). (See Table 10)

Table 10: The Percentage of Children and Adolescents 4 through 17 years of Age with Seroconversion1 and HI Titers ≥ 1:40 post vaccination with FLUCELVAX QUADRIVALENT– Per-Protocol Analysis Set2 (Study 5)

Abbreviations: HI = hemagglutinin inhibition. CI = confidence interval.

Analyses are performed on data for day 22 for previously vaccinated participants and day 50 for not previously vaccinated participants.

1 Seroconversion rate = percentage of participants with either a pre-vaccination HI titer < 1:10 and post-vaccination HI titer ≥ 1:40 or with a pre-vaccination HI titer ≥ 1:10 and a minimum 4-fold increase in post-vaccination HI titer. Immunogenicity success criteria were met if the lower limit of the 95% confidence interval (CI) of the percentage of participants with HI titer ≥ 1:40 is ≥ 70%; and the lower limit of the 95% CI of the percentage of participants with seroconversion is ≥ 40%.

2 Per protocol set: All participants in Full Analysis Set, immunogenicity population, who has correctly received the assigned vaccine, have no major protocol deviations leading to exclusion as defined prior to unblinding/ analysis and are not excluded due to other reasons defined prior to unblinding or analysis.

Study 5: NCT 01992107

A/H1N1N = 1014 A/H3N2 N = 1013 B1N = 1013 B2N = 1009
Seroconversion Rate 1 (95% CI) 72% (69-75) 47% (44-50) 66% (63-69) 73% (70-76)
HI titer ≥1:40 99% (98-100) 100% (99-100) 93% (91-94) 92% (90-93)

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