Abstract
Background.Children under 3 years of age may benefit from a double-dose of inactivated quadrivalent influenza vaccine (IIV4) instead of the standard-dose.Methods.We compared the only United States-licensed standard-dose IIV4 (0.25 mL, 7.5 µg hemagglutinin per influenza strain) versus double-dose IIV4 manufactured by a different process (0.5 mL, 15 µg per strain) in a phase III, randomized, observer-blind trial in children 6–35 months of age (NCT02242643). The primary objective was to demonstrate immunogenic noninferiority of the double-dose for all vaccine strains 28 days after last vaccination. Immunogenic superiority of the double-dose was evaluated post hoc. Immunogenicity was assessed in the per-protocol cohort (N = 2041), and safety was assessed in the intent-to-treat cohort (N = 2424).Results.Immunogenic noninferiority of double-dose versus standard-dose IIV4 was demonstrated in terms of geometric mean titer (GMT) ratio and seroconversion rate difference. Superior immunogenicity against both vaccine B strains was observed with double-dose IIV4 in children 6–17 months of age (GMT ratio = 1.89, 95% confidence interval [CI] = 1.64–2.17, B/Yamagata; GMT ratio = 2.13, 95% CI = 1.82–2.50, B/Victoria) and in unprimed children of any age (GMT ratio = 1.85, 95% CI = 1.59–2.13, B/Yamagata; GMT ratio = 2.04, 95% CI = 1.79–2.33, B/Victoria). Safety and reactogenicity, including fever, were similar despite the higher antigen content and volume of the double-dose IIV4. There were no attributable serious adverse events.Conclusions.Double-dose IIV4 may improve protection against influenza B in some young children and simplifies annual influenza vaccination by allowing the same vaccine dose to be used for all eligible children and adults.
Highlights
Children under 3 years of age may benefit from a double-dose of inactivated quadrivalent influenza vaccine (IIV4) instead of the standard-dose
Immunogenic noninferiority of double-dose versus standard-dose IIV4 was demonstrated in terms of geometric mean titer (GMT) ratio and seroconversion rate difference
Superior immunogenicity against both vaccine B strains was observed with double-dose IIV4 in children 6–17 months of age (GMT ratio = 1.89, 95% confidence interval [CI] = 1.64–2.17, B/Yamagata; GMT ratio = 2.13, 95% CI = 1.82–2.50, B/Victoria) and in unprimed children of any age (GMT ratio = 1.85, 95% CI = 1.59–2.13, B/ Yamagata; GMT ratio = 2.04, 95% CI = 1.79–2.33, B/Victoria)
Summary
We compared the only United States-licensed standard-dose IIV4 (0.25 mL, 7.5 μg hemagglutinin per influenza strain) versus double-dose IIV4 manufactured by a different process (0.5 mL, 15 μg per strain) in a phase III, randomized, observer-blind trial in children 6–35 months of age (NCT02242643). Immunogenicity was assessed in the per-protocol cohort (N = 2041), and safety was assessed in the intent-to-treat cohort (N = 2424). This was a phase III, randomized, controlled, observer-blind, multicenter trial in children 6–35 months of age The trial was approved by independent ethics committees or institutional review boards, conducted in accordance with the Declaration of Helsinki, the International Conference on Harmonisation Good Clinical Practice (ICH-GCP).
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