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The New England Journal of Medicine Publishes First-of-its-Kind Study on Cell-Based Quadrivalent Seasonal Influenza Vaccine (QIVc) Efficacy in Children and Adolescents ≥2 to <18 Years of Age

Seqirus, a global leader in influenza prevention, and a business of CSL Limited (ASX:CSL), today announced that The New England Journal of Medicine has published absolute efficacy data on the company’s cell-based quadrivalent influenza vaccine (QIVc) from a randomized controlled trial (RCT) which met its primary endpoint.1 The study indicates that the seasonal influenza vaccine was effective and produced a sufficient immune response against influenza in children and adolescents ≥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.This represents the first absolute efficacy study of a cell-based influenza vaccine in children as young as two years of age.

“In this study, QIVc demonstrated absolute efficacy in children and adolescents, showing consistent benefit across three seasons and eight countries.This is particularly impactful given  the disease burden in children as young as two years of age,” said Jonathan Edelman, MD, Vice President, Clinical Development at Seqirus and study author. “These data add to a growing body of evidence supporting the fact that our differentiated, cell-based seasonal influenza vaccine can help provide effective protection against flu.”

QIVc utilizes a cell-based influenza vaccine manufacturing process, an alternative to traditional egg-based manufacturing.Traditional egg-based vaccine production can cause the strain to mutate at several steps throughout the manufacturing process, which may lead to an antigenic mismatch between the circulating strains and the inactivated influenza strains contained within the seasonal influenza vaccine.

Cell-based influenza vaccines are designed to produce an exact match to WHO-selected influenza virus strains by avoiding egg-adapted changes, and therefore have the potential for greater vaccine effectiveness.2,3  Cell-based influenza vaccine technology may offer additional advantages over the standard influenza manufacturing process, including increased scalability and production speed in the event of an influenza pandemic.2 

“Young children are at a higher risk than adults for serious influenza-related complications.We’re particularly pleased with the results of this study because it supports the use of our differentiated, cell-based influenza vaccine technology as an effective means of influenza protection in children as young as two years old,” said Gregg Sylvester, MD, Chief Medical Officer at Seqirus. 
The results of this study supported the recent U.S. Food and Drug Administration (FDA) approval for an expanded age indication for use of QIVc in children ≥2 years of age.5 QIVc is marketed in the United States as FLUCELVAX® QUADRIVALENT (Influenza Vaccine) and is currently under review by the U.S. Food and Drug Administration (FDA) for an expanded age indication for children as young as six months of age.5

The Centers for Disease Control and Prevention (CDC), recommends annual seasonal influenza vaccination for everyone six months of age and older without contraindications as the best way to prevent seasonal influenza.It is estimated that more than 52,000 hospitalizations occurred in children younger than 18 years of age during the 2019/20 U.S. influenza season, and there were approximately over 434 influenza-related deaths in this age group.

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.Last year, Seqirus announced plans to build a new, world-class cell-based manufacturing facility in Australia, which will be the only cell-based influenza vaccine manufacturing facility in the Southern Hemisphere.9  

About the Study
This phase III/IV multi-center, randomized, observer-blind study was conducted across eight countries (Australia, Philippines, Thailand, Estonia, Finland, Lithuania, Poland, and Spain) over three influenza seasons – Southern Hemisphere (2017) and Northern Hemisphere (2017/18 and 2018/19).1

The study was designed to demonstrate the efficacy and safety of QIVc in children ≥2 to <18 years of age, compared to a non-influenza comparator.1 A total of 4514 subjects (n= 2258 QIVc, n=2256 comparator (Menveo®, meningococcal [Serogroup ACYW-135] conjugate vaccine)) were enrolled.The primary endpoint was the first occurrence of laboratory-confirmed influenzas illness (by RT-PCR or viral culture) occurring between >14 days after last vaccination and the end of the influenza season.The influenza attack rate in the QIVc group was 175/2257 (7.8%; 6.5% to 10.2% over three seasons), compared with 364/2252 (16.2%; 15.2% to 17.4% over three seasons) cases in the control group.1

The efficacy of QIVc in children and adolescents against laboratory-confirmed influenza illness was 54.6% (95% CI 45.7 to 62.1), meeting the pre-specified endpoint for success and showing benefit across three seasons and eight countries.

The safety profile of QIVc was comparable to the non-influenza comparator.1

About Seasonal Influenza
Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life- threatening complications in some people.10 Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalization and in some cases, death.10 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.10 Estimates from the CDC report that during the 2019/20 influenza season, there were an estimated 405,000 influenza-related hospitalizations in the U.S.The CDC recommends annual vaccination for individuals aged 6 months and older, who do not have any contraindications.6 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.The CDC recommends that people get vaccinated by the end of October.For non-pregnant adults, getting vaccinated too early (for example, in July or August), should be avoided, unless there is concern that later vaccination may not be possible, as it can be associated with reduced protection against influenza infection later  in the flu season.

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.

All other trademarks referenced herein are the property of their respective owners. 


Maria Tortoreto
+1 (201) 248-5208


Nolan T, Fortanier AC, Leav B, et al. Efficacy of aCell-Culture–Derived Quadrivalent Influenza Vaccine in Children. N Engl J Med. DOI: 10.1056/NEJMoa2024848

Centers for Disease Control and Prevention (CDC). (2021). Cell-Based Flu Vaccines. Retrieved from: Accessed September 2021.

Rajaram, S., Boikos, C., Gelone, et al. (2020). Influenza Vaccines: The Potential Benefits of Cell-Culture Isolation and Manufacturing. Therapeutic Advances in Vaccines and Immunotherapy. DOI: 10.1177/2515135520908121

CDC. (2021). Flu & Young Children. Retrieved from: Accessed September 2021.

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

CDC. (2021). Who Needs a Flu Vaccine and When. Retrieved from: Accessed September 2021.

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

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 HHSO10020060001F2C, HHSO100200700030C, HHSO100200900101C and HHSO100201200003I.

Data on file. (2020). Seqirus USA Inc.

10 CDC. (2021). Key Facts about Influenza (Flu). Retrieved from: Accessed September 2021.

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