• Results of the first season of a randomized study showed adjuvanted and high-dose influenza vaccines did not differ in effectiveness against PCR-confirmed influenza.
• This is the first randomized study to evaluate the relative vaccine effectiveness of adjuvanted influenza vaccines compared to high-dose influenza vaccines for prevention of lab-confirmed influenza.

SUMMIT, N.J., Oct. 18, 2024 /PRNewswire/ -- CSL Seqirus, a business of CSL (ASX: CSL), today announced the first season (2023-2024 influenza season) results of the first pragmatic randomized study to evaluate the relative vaccine effectiveness (rVE) of adjuvanted inactivated influenza vaccine (aIIV) compared to high-dose inactivated influenza vaccine (HD-IIV) for prevention of lab-confirmed influenza. Results for the first season demonstrated that adjuvanted and high-dose influenza vaccines did not differ in effectiveness against Polymerase Chain Reaction (PCR)-confirmed influenza with a rVE of aIIV vs HD-IIV of 1.5% (95% confidence interval: -8.4 to 10.5) among adults 65 years of age and older. In addition, there was no difference in effectiveness between aIIV and HD-IIV for the prevention hospitalization or emergency department visits for PCR-confirmed influenza, and hospitalization for all-cause community-acquired pneumonia.

This study is a collaborative study between CSL Seqirus and a large health system. The data was presented during an oral presentation this week at the IDWeek 2024 conference taking place in Los Angeles, California from October 16-19, 2024.

The current findings of this pragmatic study align with previous research based on diagnostic and test confirmed outcomes, systematic reviews and meta-analyses which have generally shown comparable effectiveness between aIIV and HD-IIV influenza vaccines. The findings also support the current U.S. Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices (ACIP) recommendation that preferentially recommends any adjuvanted or higher-dose influenza vaccines for adults 65 years of age and older.

The collaborative study is being conducted as a two-season pragmatic randomized study with approximately 480,000 individuals 65 years of age and older anticipated each season throughout facilities within a large health system. The second season and pooled season analyses will be performed following the end of the 2024-2025 season.

"The findings of the first season of this study align with previous research based on diagnostic and test confirmed outcomes and systematic reviews and meta-analyses, which have shown comparable effectiveness between adjuvanted and high-dose influenza vaccines," says Ian McGovern, Associate Director, Center of Outcomes Research and Epidemiology. "Further, this data showcases the commitment of CSL Seqirus in generating high-quality real-world evidence data (RWE)."

About the Study

This study was a collaborative effort between CSL Seqirus and a large health maintenance organization within Northern California that both provides insurance and health care to their patient population.

Individual medical facilities are randomized to administer either aIIV or HD-IIV and in alternating weeks which allowed individuals to be vaccinated as they would in routine clinical practice. Vaccinated individuals are tested for influenza per routine care using PCR for all tests.

The study is designed to test the hypothesis that aIIV is non-inferior to HD-IIV, with a non-inferiority margin of -20% (i.e., lower bound of 95% CI needs to be above -20%). The primary outcome is PCR confirmed influenza in any setting. Secondary outcomes in each season include prevention of hospitalization or emergency department visits for PCR-confirmed influenza, and hospitalization for all-cause community-acquired pneumonia. A pooled analysis of the two seasons additionally includes the outcome of hospitalized PCR-confirmed influenza as well as analysis by age and risk groups.

A total of 429,600 individuals were enrolled in the study for the first season: 212,877 adjuvanted inactivated influenza vaccine (aIIV); 216,723 high-dose inactivated influenza vaccine (HD-IIV). The randomization combined with broad patient inclusion results in a more representative but still balanced study population compared to a typical clinical study.

The second season of the study is ongoing. Results may differ depending on the match between the vaccine and circulating influenza strains and other factors. This study was funded by CSL Seqirus. CSL Seqirus provided all the adjuvanted influenza vaccine doses to members of a large health system for this study.

About Seasonal Influenza

Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life-threatening complications in some people.¹ Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalization and in some cases, death.¹ 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.¹ Preliminary estimates from the Centers for Disease Control and Prevention (CDC) report that during the 2023/24 influenza season, there were an estimated 390,000-830,000 influenza-related hospitalizations in the U.S.² The CDC recommends annual vaccination for people aged six months and older, who do not have any contraindications.³ 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 for most people who need only 1 dose of influenza vaccine, vaccination should ideally happen in September or October.³

About CSL Seqirus

CSL Seqirus is part of CSL (ASX: CSL). As a global leader in the protection of public health and one of the largest influenza vaccine providers in the world, CSL Seqirus is committed to preventing infectious diseases, like influenza and COVID-19, and is 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, CSL Seqirus offers a broad portfolio of innovative, differentiated vaccines in more than 20 countries around the world.

For more information about CSL Seqirus, visit www.CSL.com.

About CSL

CSL (ASX:CSL; USOTC:CSLLY) is a global biotechnology company with a dynamic portfolio of lifesaving medicines, including those that treat haemophilia and immune deficiencies, vaccines to prevent influenza, and therapies in iron deficiency and nephrology. Since our start in 1916, we have been driven by our promise to save lives using the latest technologies. Today, CSL – including our three businesses: CSL Behring, CSL Seqirus and CSL Vifor – provides lifesaving products to patients in more than 100 countries and employs 32,000 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 inspiring stories about the promise of biotechnology, visit csl.com/we-are-csl/vita-original-stories and follow us on x.com/CSL.

For more information about CSL, visit www.CSL.com.

Intended Audience

This press release is issued from CSL Seqirus 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 CSL Seqirus products may vary from country to country. Please consult your local regulatory authority on the approval status of CSL 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

Tiffany Cody

+1 (908) 370-1863

Tiffany.Cody@Seqirus.com

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