FDA Approves Flublok Quadrivalent Flu Vaccine


The US Food and Drug Administration has approved its quadrivalent formulation of the Flublok influenza vaccine.

On October 11, 2016, Protein Sciences Corporation announced that the US Food and Drug Administration (FDA) had approved its quadrivalent formulation of the Flublok influenza vaccine. Like the trivalent vaccine, Flublok Quadrivalent provides protection against 2 strains of influenza A and 1 lineage of influenza B. However, unlike the trivalent vaccine, Flublok Quadrivalent provides protection against an additional lineage of influenza B.1,2

In the United States, most influenza vaccines are currently produced using eggs. Two vaccines (Flublok and Flucelvax) are produced using cell culture. In the manufacture of Flucelvax, influenza virus is produced using cultured canine cells and cultured viruses are then inactivated. Unlike Flucelvax, Flublok is produced through a cell culture of insect-derived cells that are genetically engineered to express only the surface antigens of the influenza virus. Due to the fact that only surface antigens are expressed, there is no virus inactivation step as there is with all other forms of the influenza vaccine, including Flucelvax.1-3

As a result of this unique manufacturing process, Flublok Quadrivalent does not contain antibiotics, eggs, thimerosal, preservatives, gelatin, or latex, and is engineered to deliver 3 times more antigen per dose than existing quadrivalent vaccines. Presence of this additional antigen has been shown to confer additional efficacy against influenza.1,2

In a 9000-patient clinical study of adults aged 50 years and older, compared with a quadrivalent influenza vaccine produced using eggs, use of Flublok Quadrivalent reduced the likelihood of developing influenza by more than 40%. This improvement in efficacy has been linked to improved protective efficacy against influenza A H3N2 infection.1,4

The improved protective efficacy of Flublok Quadrivalent against influenza A H3N2 may relate to challenges in the production of H3N2 with traditional egg-based vaccines. Because influenza A H3N2 grows poorly in eggs, manufacturers rely on egg-adapted strains of H3N2 that may be different from strains circulating in the environment. Manufacture of Flublok Quadrivalent is not subject to these challenges.1,2,5

Although the high-dose influenza vaccine (Fluzone High-Dose) and the adjuvanted influenza vaccine (Fluad) are indicated for use in adults aged 65 or older, neither of these vaccines are available in a quadrivalent form. Flublok Quadrivalent will offer older adults a quadrivalent option that contains more antigen than existing quadrivalent influenza vaccines.1,2,6,7

Flublok Quadrivalent is not yet commercially available. For the 2016-2017 season, only trivalent Flublok will be available. In a press release, President and CEO of Protein Sciences Corporation, Manon Cox, stated “We are looking forward to launching the vaccine next year and, in the meantime, continuing to make trivalent Flublok available this year.”1

As with all influenza vaccines, use of Flubok Quadrivalent is contraindicated in patients who have previously experienced a severe allergic reaction to any component of the vaccine. Common adverse reactions include injection site reactions, headache, and fatigue. For complete information please consult the product package insert.2


1. Protein Sciences Corporation. FDA Approves Flublok Quadrivalent Influenza Vaccine. Flublok website. www.flublok.com/media/1126/quad-approval-final.pdf. Published October 11, 2016. Accessed September 2016.

2. Flublok Quadrivalent (influenza vaccine) [package insert]. Meriden, CT: Protein Sciences Corporation; 2016.

3. Flucelvax Quadrivalent (influenza vaccine) [package insert]. Holly Springs, NC: Sequirus, Inc; 2016.

4. Cox MM, Izikson R, Post P, Dunkle L. Safety, efficacy, and immunogenicity of Flublok in the prevention of seasonal influenza in adults. Ther Adv Vaccines. 2015;3(4):97-108.

5. Centers for Disease Control and Prevention. Selecting viruses for the seasonal influenza vaccine. www.cdc.gov/flu/about/season/vaccine-selection.htm. Updated May 4, 2016. Accessed October 2016.

6. FLUAD (Influenza Vaccine, Adjuvanted) [package insert]. Holly Springs, NC: Sequirus, Inc; 2016.

7. FLUZONE HIGH-DOSE (influenza vaccine) [package insert]. Swiftwater, PA: Sanofi Pasteur, Inc; 2016.

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