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Seqirus Announces U.S. FDA Approval of Expanded Age Indication of Its Cell-Based Quadrivalent Influenza Vaccine for People Two Years of Age and Older

Seqirus, a global leader in influenza prevention, today announced that the U.S. Food and Drug Administration (FDA) has approved FLUCELVAX® QUADRIVALENT (Influenza Vaccine), the company’s cell-based quadrivalent influenza vaccine (QIVc), for an expanded age indication for people two years of age and older.[1] FLUCELVAX QUADRIVALENT was previously FDA-approved for use in persons four years of age and older. FLUCELVAX QUADRIVALENT will be available as a 0.5ml intramuscular (IM) vaccine per dose for the 2021/22 U.S. influenza season.

The expanded age indication is based on absolute efficacy data indicating that FLUCELVAX QUADRIVALENT was effective and produced a sufficient immune response against influenza in children and adolescents between ≥2 to <18 years of age over three influenza seasons in the Southern (2017) and Northern (2017/18 and 2018/19) Hemispheres, compared to a non-influenza comparator.[2] This represents the first absolute efficacy study of a cell-based influenza vaccine in this population. 

“Young children are at a high risk of complications from influenza, which is why annual vaccination is critical,” said Gregg Sylvester, MD, Chief Medical Officer at Seqirus. “The absolute efficacy results for FLUCELVAX QUADRIVALENT that served as the basis for this approval indicate that the cell-based vaccine offers an important new option for children as young as two years of age.”

According to the Centers for Disease Control and Prevention (CDC), the best way to prevent influenza is by receiving an annual seasonal influenza vaccine.[3] More than 52,000 hospitalizations occurred in children aged 18 years of age and younger during the 2019/20 U.S. influenza season, and there were over 434 influenza-related deaths in this age group.[4] Children younger than five years of age are at high risk of developing serious flu-related complications.[5] The CDC recommends everyone six months of age and older without contraindications receive an influenza vaccine annually.3

FLUCELVAX QUADRIVALENT utilizes a cell-based influenza vaccine manufacturing process, an alternative to traditional egg-based manufacturing. There are several factors that can impact seasonal influenza vaccine effectiveness, which may include mismatch between circulating strains and the influenza strains contained within the seasonal influenza vaccine. Egg-based manufacturing requires a growth-inducing strain to ensure the influenza virus can grow successfully in eggs, which can cause the strain to mutate and result in an influenza virus that can be different from the intended strain.[6] This may lead to a mismatch between the circulating strains and the inactivated influenza strains contained within the seasonal influenza vaccine.6 Cell-based influenza vaccines like FLUCELVAX QUADRIVALENT are designed to help avoid egg-adapted changes and may result in vaccine virus strains that are more closely matched to those selected by the World Health Organization.6,[7] Cell-based influenza vaccine technology may offer additional advantages over the standard influenza manufacturing process, including being more scalable and offering faster production in the event of an influenza pandemic.6

“While influenza vaccination has always offered a way to minimize the burden of disease on the healthcare system, it is more important than ever this season to minimize the burden on the healthcare system and preserve capacity for COVID-19 patients,” said Dave Ross, Vice President, North America Commercial Operations at Seqirus. “Especially now, we remain focused on our public health imperative to help protect as many people as possible against influenza, especially children.”

In the U.S., Seqirus operates a state-of-the-art cell-based manufacturing facility in Holly Springs, North Carolina, purpose-built in partnership with the Biomedical Advanced Research and Development Authority (BARDA) to increase cell-based vaccine manufacturing capacity and combat pandemic influenza threats.[8]

Seqirus plans to continue exploring other clinical research associated with FLUCELVAX QUADRIVALENT.

About Seasonal Influenza
Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life- threatening complications in some people.[9] Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalization and in some cases, death.9 The CDC recommends annual vaccination for individuals aged 6 months and older, who do not have any contraindications.3 Because transmission of influenza viruses to others may occur one day before symptoms develop and up to 5 to 7 days after becoming sick, the disease can be easily transmitted to others.9 Preliminary estimates from the CDC report that from October 1, 2019, through April 4, 2020, there were an estimated 410,000 to 740,000 influenza-related hospitalizations in the U.S.[10] Since it takes about two weeks after vaccination for antibodies to develop in the body that help protect against influenza virus infection, it is recommended that people get vaccinated before influenza begins spreading in their community.3 The CDC recommends that people get vaccinated by the end of October.[11] Getting vaccinated too early (for example, in July or August), can be associated with reduced protection against influenza infection later in the flu season.11 However, getting vaccinated later can still be beneficial and vaccination should continue to be offered throughout the influenza season, even into January or later.11

About Seqirus
Seqirus is part of CSL Limited (ASX: CSL). As one of the largest influenza vaccine providers in the world, Seqirus is a major contributor to the prevention of influenza globally and a transcontinental partner in pandemic preparedness. With state-of-the-art production facilities in the U.S., the U.K. and Australia, and leading R&D capabilities, Seqirus utilizes egg, cell and adjuvant technologies to offer a broad portfolio of differentiated influenza vaccines in more than 20 countries around the world.

About CSL
CSL (ASX:CSL) is a leading global biotechnology company with a dynamic portfolio of life-saving medicines, including those that treat hemophilia and immune deficiencies, as well as vaccines to prevent influenza. Since our start in 1916, we have been driven by our promise to save lives using the latest technologies. Today, CSL — including our two businesses, CSL Behring and Seqirus - provides life- saving products to more than 100 countries and employs more than 27,000 people. Our unique combination of commercial strength, R&D focus and operational excellence enables us to identify,develop and deliver innovations so our patients can live life to the fullest. For more information about CSL Limited, visit

For more information visit and

Intended Audience
This press release is issued from Seqirus USA Inc. in Summit, New Jersey, USA and is intended to provide information about our global business. Please be aware that information relating to the approval status and labels of approved Seqirus products may vary from country to country. Please consult your local regulatory authority on the approval status of Seqirus products.

Forward-Looking Statements
This press release may contain forward-looking statements, including statements regarding future results, performance or achievements. These statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements.



What is FLUCELVAX® QUADRIVALENT (Influenza Vaccine)?
FLUCELVAX QUADRIVALENT is a vaccine that helps protect people aged 2 and older from the flu. Vaccination with FLUCELVAX QUADRIVALENT may not protect all people who receive the vaccine.

You should not get FLUCELVAX QUADRIVALENT if you have had a severe allergic reaction to any of the ingredients in the vaccine.

Before receiving FLUCELVAX QUADRIVALENT, tell your healthcare provider about all medical conditions, including if you:
• have ever had Guillain-Barré syndrome (severe muscle weakness) within six weeks after getting a flu vaccine. The decision to give FLUCELVAX QUADRIVALENT should be made by your healthcare provider, based on careful consideration of the potential benefits and risks.
• have problems with your immune system or are taking certain medications that suppress your immune system, as these may reduce your immune response to the vaccine
• have ever fainted when receiving a vaccine

What are the most common side effects of FLUCELVAX QUADRIVALENT?
• pain, redness, or a raised hardened area or swelling where the vaccine was given
• headache
• tiredness
• muscle aches
• feeling unwell (malaise)

Additional side effects seen in children include:
• tenderness or bruising where vaccine was given
• sleepiness
• irritability
• changes in eating habits

These are not all of the possible side effects of FLUCELVAX QUADRIVALENT. You can ask your healthcare provider for more information and for advice about any side effects that concern you.
To report SUSPECTED ADVERSE REACTIONS, contact Seqirus at 1 855 358-8966 or VAERS at 1‐800‐822‐7967 or
You are also encouraged to report negative side effects of prescription drugs to the FDA. Visit or call 1‐800‐FDA‐1088.
Before receiving this vaccine, please see the full US Prescribing Information for FLUCELVAX QUADRIVALENT. The information provided here does not include all that is known about FLUCELVAX QUADRIVALENT. To learn more, talk with your healthcare provider or pharmacist. 

FLUCELVAX® QUADRIVALENT is a registered trademark of Seqirus UK Limited or its affiliates. USA-QIVc-21-0006

Polina Miklush
+1 (908) 608-7170

[1] FLUCELVAX® QUADRIVALENT (Influenza Vaccine) [package insert]. Holly Springs, NC: Seqirus Inc; 2021.

[2] Fortanier, A.C., Põder, A., Bravo, L.C., et al. (2020). Efficacy of Cell-Derived Quadrivalent Influenza Vaccine Against Clinical Influenza in Children 2 to <18 Years of Age. 

[3] The Centers for Disease Control and Prevention (CDC). (2020). Key Facts About Seasonal Flu Vaccine. Retrieved from: Accessed March 2021.

[4] CDC. (2020). Estimated Influenza Illnesses, Medical visits, Hospitalizations, and Deaths in the United States — 2019–2020 Influenza Season. Retrieved from: Accessed March 2021.

[5] Centers for Disease Control and Prevention (CDC). (2020). Flu & Young Children. Retrieved from: Accessed March 2021.

[6] CDC (2020). Cell-Based Flu Vaccines. Retrieved from: Accessed March 2021.

[7] Rajaram, S., Boikos, C., Gelone, et al. (2020). Influenza Vaccines: The Potential Benefits of Cell-Culture Isolation and Manufacturing.

[8] This project has been funded in whole or in part with Federal funds from the Office of the Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority, under contract numbers HHSO100200600012C, HHSO100200700030C, HHSO100200900101C and HHSO100201200003I.

[9] CDC. (2019). Key Facts about Influenza (Flu). Retrieved from: Accessed March 2021.

[10] CDC. (2020). 2019-2020 U.S. Flu season: Preliminary burden estimates. Retrieved from: Accessed September 2020. Accessed March 2021.

[11] CDC. (2020). Who Needs a Flu Vaccine and When. Retrieved from: Accessed March 2021.