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Seqirus Presents New Safety Data Demonstrating Safety of Cell-Based Seasonal Influenza Vaccine on Pregnancy Outcomes

Findings from a new observational safety study conducted in the U.S. found no unexpected adverse pregnancy outcomes in pregnant people who were vaccinated with the cell-based quadrivalent seasonal influenza vaccine during pregnancy.


Seqirus, a global leader in influenza prevention and a business of CSL Limited (ASX:CSL), presented findings from a new observational safety study conducted in the U.S. that found no unexpected adverse pregnancy outcomes in pregnant people who were vaccinated with the company’s cell-based quadrivalent seasonal influenza vaccine (QIVc) during pregnancy.1  These data were presented at the Infectious Diseases Society for Obstetrics and Gynecology (IDSOG) Meeting on July 30, 2021. 

The prospective observational cohort study evaluated pregnancy outcomes and events of interest in the fetus or infant following vaccination with QIVc during any trimester.1 The findings from this study were reviewed by an independent Scientific Advisory Committee (SAC).1

“Pregnant people and people who have recently given birth can be particularly vulnerable to infectious diseases like influenza,” said Christopher Robinson, MD, MSCR, Charleston Maternal Fetal Medicine and study author. “These data provide further reassurance on the safe use of seasonal influenza vaccines in pregnant people.”

Pregnant people are considered an at-risk population for influenza.2  Changes that occur in the immune system, heart and lungs during pregnancy can make those who are pregnant, and those who are up to two weeks postpartum, more prone to severe illness or complications from influenza.2   Influenza vaccination is the best way to prevent influenza and the Centers for Disease Control and Prevention (CDC) recommends seasonal influenza vaccine every year as the best way to prevent influenza for everyone six months of age and above who do not have contraindications.3  This recommendation extends to pregnant people as well.2 

“These data provide additional safety information with regards to unexpected pregnancy complications and/or fetal outcomes to healthcare providers considering vaccination to protect their pregnant patients from the flu,” said Josephine van Boxmeer, lead Clinical Scientist for the study at Seqirus and an author. “We are committed to helping to protect as many people as possible against influenza, including those who are pregnant.”

These clinical data are an addition to a growing body of evidence supporting the safety and utility of cell-based influenza vaccines like QIVc.4  The cell-based influenza vaccine, marketed in the U.S. as FLUCELVAX® QUADRIVALENT, is approved in the U.S. for use for the prevention of influenza disease in people two years and older and is currently under review with the U.S. Food and Drug Administration (FDA) for an expanded age indication for children as young as six months of age.5 

QIVc utilizes a cell-based influenza vaccine manufacturing process, an alternative to traditional egg-based manufacturing.6  Cell-based influenza vaccines are designed to produce an exact match 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 

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  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 prospective observational cohort study evaluated pregnancy outcomes and events of interest in the fetus or infant, including major congenital malformation (MCM), preterm birth and low birth weight, following vaccination with QIVc during any trimester.1 The study included pregnant people in the U.S. in routine clinical care settings, using five OB/GYN clinics, during three Northern Hemisphere influenza seasons (2017/18, 2018/19, and 2019/20).1

Of the 693 persons identified for the study, 3.9% were lost to follow-up, leaving 665 persons in the primary analysis population (PAP).1 Among all enrolled persons (n=693), 196 (28.3%) were exposed to QIVc in their first trimester, 286 (41.3%) were exposed during their second trimester and 211 (30.4%) were exposed in their third trimester.1

The findings from this study, which were reviewed by an independent Scientific Advisory Committee (SAC), showed no unexpected patterns of pregnancy complications and/or adverse fetal outcomes when pregnant people were vaccinated with QIVc.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 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.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.11  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.12  The CDC recommends that people get vaccinated by the end of October.12 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.3 However, getting vaccinated later can still be beneficial and vaccination should continue to be offered throughout the influenza season, even into January or later.12

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

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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. 


Polina Miklush
+1 (908) 608-7170


1. Albano, J., van Boxmeer,J., Tilson, H., et. al. (2021). A Prospective Cohort Study on Pregnancy Outcomes in Women Immunized with Seasonal Cell Culture-Derived Quadrivalent Influenza Vaccine (QIVc) During Pregnancy. Presented at Infectious Diseases Society for Obstetrics and Gynecology 2021. 

2. CDC. (2021). Flu & Pregnant Women. Retrieved from: Accessed July 2021.

3. CDC. (2021). WG Considerations and Proposed Influenza Vaccine Recommendations, 2021-22 . Retrieved from: Accessed July 2021.

4. Bart S., Cannon K., Herrington D. et al. Immunogenicity and safety of a cell culture-based quadrivalent influenza vaccine in adults: A Phase III, double-blind, multicenter, randomized, non-inferiority study. Human Vaccines & Immunotherapies 2016;12 (9):2278-88.

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

6. CDC. (2020). Cell-Based Flu Vaccines. Retrieved from: Accessed April 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 HHSO10020060001F2C, HHSO100200700030C, HHSO100200900101C and HHSO100201200003I.

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

10. CDC. (2019). Key Facts about Influenza (Flu). Retrieved from: Accessed April 2021.

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

12. CDC. (2020). Who Needs a Flu Vaccine and When. Retrieved from: Accessed April 2021.