The Food and Drug Administration (FDA) has approved Audenz (influenza A [H5N1] monovalent vaccine; Seqirus) for active immunization for the prevention of disease in patients 6 months of age and older at increased risk of exposure to the influenza A H5N1 virus subtype contained in the vaccine.

Audenz is an inactivated cell-based influenza vaccine that contains the proprietary adjuvant MF59, an oil-in-water squalene-based emulsion; vaccine adjuvants are used to enhance and prolong immune responses. In a statement, Seqiris noted that the MF59 adjuvant “is an important part of pandemic preparedness planning as it reduces the amount of antigen required to produce an immune response, increasing the number of doses of vaccine developed, so that a large number of people can be protected as quickly as possible.”

The effectiveness of Audenz was based on data from a phase 3 placebo-controlled trial that evaluated the vaccine in 3196 adults 18 years of age and older. Patients were randomized 3:1 to receive either 2 doses of Audenz or placebo, 21 days apart;  hemagglutination-inhibition (HI) antibody titers against the A/turkey/Turkey/1/2005 (H5N1) strain were evaluated in sera obtained 21 days after the second dose. Success was defined as the the proportion of individuals with seroconversion ≥40% in patients 18 to 64 years or ≥30% for those ≥65 years, as well as the proportion of patients with HI titer ≥ 1:40 in ≥70% of patients 18 to 64 years old or ≥60% for those ≥65 years.

Results showed the proportion of patients 18 to 64 years of age with seroconversion or HI titer ≥ 1:40 was 79.9% and 95.0% with Audenz, compared with 0.3% and 8.5% with placebo, respectively. In adults 65 years of age and older, the proportion of patients with seroconversion or HI titer ≥ 1:40 was 54.0% and 85.7% with Audenz and 1.7% and 20.8% with placebo, respectively. 

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Additionally, in a study evaluating the vaccine in patients 6 months through 17 years (N=289), the prespecified criteria for the proportions of patients with seroconversion and an HI titer ≥ 1:40 were met at 21 days after the second vaccination with Audenz. Use in this patient population was approved under accelerated approval; continued approval for use in this age group may be contingent upon verification and description of clinical benefit in confirmatory trials.

The vaccine is administered intramuscularly as a 2-dose regimen, 21 days apart. Each 0.5mL dose is supplied in a prefilled single-dose syringe.

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