Seqirus Co-Authors First Study to Assess Simultaneous Administration of Seasonal Influenza Vaccine and COVID-19 Vaccine Candidate

Seqirus, a global leader in influenza prevention and a division of CSL Limited (ASX: CSL), today announced that the company co-authored the first study to demonstrate the safety, immunogenicity and efficacy profile of a COVID-19 vaccine when co-administered with a seasonal influenza vaccine

SUMMIT, N.J., June 14, 2021 /PRNewswire/ -- Seqirus, a global leader in influenza prevention and a division of CSL Limited (ASX: CSL), today announced that the company co-authored the first study to demonstrate the safety, immunogenicity and efficacy profile of a COVID-19 vaccine when co-administered with a seasonal influenza vaccine.1 The data is now available on medRxiv ahead of peer-review publication.1

The study was conducted by Novavax, Inc. as part of a Phase 3 clinical trial of NVX-CoV2373, its recombinant protein COVID-19 vaccine candidate, in the United Kingdom.1 The co-administration sub-study enrolled 431 volunteers, all of whom received either an adjuvanted, trivalent seasonal influenza vaccine (aTIV) or a cell-based, quadrivalent seasonal influenza vaccine (QIVc) provided by Seqirus.1 Approximately half of the volunteers also received NVX-CoV2373 while the remainder received the placebo. The study results suggest that efficacy of both the influenza vaccine and the COVID-19 vaccine candidate appeared to be preserved.1 No additional safety concerns were found with co-administration and adverse events were similar to the incidence and severity for each vaccine when administered separately.1

“These data could be used to help inform guidance or recommendations on the co-administration of influenza and COVID-19 vaccines, overcoming challenges and contributing towards a new normal to protect at-risk populations from both infections,” said Raja Rajaram, M.D., Medical Affairs Lead, EMEA, Seqirus, a co-author of the study. “Seqirus is committed to advancing the science underpinning influenza and taking our place on the front line, alongside our public health partners, as a reliable influenza vaccine supplier.”

Seqirus’ seasonal influenza vaccines have a well-established safety profile, and although additional research is needed, results of this study suggest that concomitant vaccination may be a viable immunization strategy.1 Participation in this co-administration study demonstrates the company’s commitment to supporting informed, science-based decisions regarding vaccinations for patients.

Study limitations include the small size of the sub-study, lack of formal pre-specified non-inferiority statistical assessment of immunogenicity, and the lack of randomization in recruiting the influenza sub-study, immunogenicity and reactogenicity cohorts.1

“With large scale COVID-19 vaccination campaigns underway in many countries across the globe, and as mitigation tactics like social distancing become more relaxed, we need to be prepared for the resurgence of influenza activity,” said Gregg Sylvester, M.D., Chief Medical Officer at Seqirus. “As a company on the front line of influenza prevention, we’re committed to helping protect our communities with our differentiated portfolio of safe and effective influenza vaccines.”

Seqirus appreciates the opportunity to partner with Novavax on this important study.

“As the next influenza season approaches and people still need a primary COVID-19 vaccine series or a booster, separate healthcare visits to cover both COVID-19 and influenza vaccinations will be burdensome,” said Gregory M. Glenn, M.D., President of Research and Development, Novavax. “As the first clinical study to evaluate safety, immunogenicity, and efficacy of a COVID-19 vaccine when co-administered with a seasonal influenza vaccine, these results demonstrate the promising opportunity for concomitant vaccination, which may improve the uptake of both vaccines.”

Seqirus produces influenza vaccines across its global manufacturing network, which includes facilities in the U.S., U.K. and Australia. Since the start of the COVID-19 pandemic, the company has experienced record demand for influenza vaccines across all markets and has extended production across its three manufacturing sites.

About Seasonal Influenza
Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life-threatening complications in some people.2 Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalization and in some cases, death.2 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.2 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.4 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.5 The CDC recommends that people get vaccinated by the end of October.5 Getting vaccinated too early (for example, in July or August), can be associated with reduced protection against influenza infection later in the flu season.5 However, getting vaccinated later can still be beneficial and vaccination should continue to be offered throughout the influenza season, even into January or later.5

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.


Media Contact
Maria Tortoreto
+1 (201) 248-5208


1 Safety, Immunogenicity, and Efficacy of a COVID-19 Vaccine (NVX-CoV2373) Co-administered
With Seasonal Influenza Vaccines. (2021). medRxiv. Retrieved from: Accessed June 2021.

2 CDC. (2019). Key Facts about Influenza (Flu). Retrieved from: Accessed June 2021.

3 CDC. (2020). Key Facts About Seasonal Flu Vaccine. Retrieved from: Accessed June 2021.

4 CDC. (2020). 2019-2020 U.S. Flu season: Preliminary burden estimates. Retrieved from: Accessed June 2021.

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

Cision View original content:

SOURCE Seqirus

Company Codes: Australia:CSL, OTC-PINK:CSLLY