The Food and Drug Administration has expanded the approval of Flucelvax® Quadrivalent (influenza vaccine) for active immunization in patients 6 months of age and older against influenza disease caused by influenza virus subtypes A and type B contained in the vaccine. Previously, the vaccine was approved for patients 2 years of age and older.

Flucelvax Quadrivalent is a subunit influenza vaccine manufactured using cell derived candidate vaccine viruses; it does not contain egg proteins or antibiotics.

The expanded approval was based on data from a randomized, observer-blind, multicenter phase 3 study that compared the immunogenicity and safety of Flucelvax Quadrivalent to a US-licensed comparator quadrivalent influenza vaccine in 2402 patients aged 6 months to less than 4 years. Immune response to each vaccine antigen was assessed 28 days after last vaccination.

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Findings showed that Flucelvax Quadrivalent was noninferior to the comparator quadrivalent influenza vaccine; noninferiority was established for all 4 influenza strains and with respect to seroconversion rates 4 weeks following vaccination. 

Flucelvax Quadrivalent is supplied in 0.5mL single-dose prefilled syringes and 5mL multi-dose vials for the 2021-2022 influenza season.


  1. Seqirus receives FDA approval of its cell-based quadrivalent influenza vaccine, expanding the age indication to include children as young as six months. News release. Seqirus. Accessed October 15, 2021.
  2. Flucelvax Quadrivalent. Package insert. Seqirus; 2021. Accessed October 15, 2021.

This article originally appeared on MPR