CSL Seqirus, a global leader in seasonal influenza prevention (ASX: CSL), has shared new actionable real-world evidence (RWE) reinforcing the critical role of enhanced influenza vaccines in preventing influenza and reducing the risks of severe disease at the 10th European Scientific Working group on Influenza (ESWI) conference in Valencia.
Montreal, Quebec 24 Nov 2025
The evidence from Nordic countries underscores the importance of enhanced influenza vaccines (EIVs) for adults aged 65 and older, and suggests the need for countries across Europe to adopt or expand policies supporting their use.2 Recent studies show that both adjuvanted quadrivalent influenza vaccines (aQIV) and high-dose quadrivalent influenza vaccines (HD-QIV) offer comparable protection against influenza, building on previous data showing superior effectiveness of these vaccines compared with standard-dose vaccines in older adults.3
Key Findings on Enhanced Vaccines
A recent test-negative design study in U.S. adults aged 65+ evaluated the relative effectiveness of aQIV versus HD-QIV in preventing influenza and related hospitalizations during the 2023–2024 season:1
• Analysis included 37,377 vaccinated adults, with 3,174 testing positive for influenza.
• Relative vaccine effectiveness (rVE) between aQIV and HD-QIV was comparable: -0.9% (95% CI: -9.9, 7.3) across all settings and 0.5% (95% CI: -12.1, 11.6) in emergency or inpatient settings.
• Pooled analyses with prior seasons (2022–2023) confirmed similar effectiveness among overall and high-risk older adults.
“These results confirm that both adjuvanted and high-dose influenza vaccines are highly effective, giving health authorities flexibility to choose the best option for their populations,” said Pepe Meseguer Perez, Spain and Iberian Cluster Head at CSL Seqirus. “Importantly, previous studies have shown these enhanced vaccines outperform standard-dose formulations, providing stronger protection for older adults.”
Public Health and Economic Benefits of Expanded EIV Programs
A model-based analysis across Nordic countries (Denmark, Sweden, Norway, Finland) evaluated the impact of extending EIV coverage to all adults aged 65 and older:2
• Expanding enhanced vaccine programs would substantially reduce influenza-related GP visits, emergency visits, and hospitalizations.
• Denmark’s early adoption of EIVs for adults aged 70+ in the 2024–2025 season demonstrated measurable improvements in outcomes compared to other Nordic countries.
• Further expansion to include all adults aged 65+ could yield even greater reductions in healthcare burden and associated costs.
“These data highlight a clear opportunity for European policymakers: adopting enhanced influenza vaccines or expanding their programs for older adults to include these – not only improves health outcomes but also reduces pressure on healthcare systems,” said Lorna Meldrum, Vice President Commercial Operations, International & Pandemic Response at CSL Seqirus.
Policy Implications
With an aging population and persistent influenza risk, EIVs represent a key tool in protecting older adults. Evidence supports:
• Prioritizing adjuvanted or high-dose vaccines over standard-dose vaccines for adults aged 65 and older.
• Expanding vaccination programs to achieve broader population coverage, as demonstrated in Nordic countries.
• Strengthening influenza prevention policies across Nordic countries to reduce disease burden, hospitalizations, and healthcare costs.
About FLUAD®
FLUAD® is an adjuvanted trivalent influenza vaccine specifically designed for adults aged 65 and older. These new data support the strategic importance of FLUAD® and other enhanced vaccines in improving outcomes for older populations. Data for FLUAD® QUADRIVALENT are relevant to FLUAD® because both vaccines are manufactured using the same process and have overlapping compositions.
ABOUT THE STUDIES PRESENTED AT ESWI
Comparable Vaccine Effectiveness of Adjuvanted and High-Dose Influenza Vaccines in Preventing Test-Confirmed Influenza Outcomes, including Hospitalization, in Overall and High-Risk Older Adults: A Test-Negative Design Study During 2022–2023 and 2023–2024:
This study focused on older adults, who face a higher risk of severe flu complications, and evaluated the effectiveness of adjuvanted quadrivalent (aQIV) versus high-dose quadrivalent influenza vaccines (HD-QIV) in preventing flu and related hospitalisations. Building on previous findings from 2017–2020 and 2022–2023, the study assessed relative vaccine effectiveness (rVE) during the 2023–2024 season.1
Conducted as a retrospective test-negative design (TND) study, it included U.S. adults aged 65 and older who received either aQIV or HD-QIV and sought treatment for acute respiratory or febrile illness in emergency or inpatient settings. The research used a robust statistical model to adjust for potential confounding factors and estimate rVE.1
The study analysed data from 37,377 vaccinated patients, with 3,174 testing positive and 34,203 testing negative for influenza. The results showed comparable effectiveness between aQIV and HD-QIV, with an rVE of -0.9% 95% CI: [-9.9, 7.3]) in any setting and 0.5% (-12.1, 11.6) in emergency/inpatient settings. Pooled analysis for the 2022–2023 and 2023–2024 seasons also showed similar effectiveness in inpatient settings, both overall and in high-risk groups.1
Cost Analysis of Enhanced Influenza Vaccination in Adults Aged >65 years Compared to Current Programs Across the Nordic Region:
The objective was to compare and assess the public health impact and healthcare costs of current influenza vaccination programs versus the expanded use of universal enhanced influenza vaccines (EIVs) in adults aged 65 years and older in Nordic countries. Data shows the importance of enhanced influenza vaccines (EIV).2
Model-based estimates for Denmark, Sweden, Norway and Finland, found expanding EIVs to all individuals aged 65 years or older would significantly reduce influenza-related health burden and costs across the Nordic region by lowering influenza-related GP visits, emergency room visits, and hospitalisations.2
Improved outcomes have already been observed in Denmark for the 2024-25 season ending March 4, 2025, due to expanded EIV use to those 70 years and older. This was observed in the study when comparing Denmark to the other Nordic countries highlighting benefits of expanded use of EIVs over SD-IVs. Yet, significant improvement in outcomes could still be obtained by expanding the program in Denmark from 70 years and above to include people 65 years and older.2
These results support further expansion of EIV programs across all Nordic countries to maximise protection in ageing populations.2
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About Seasonal Influenza
Influenza is a common, contagious seasonal respiratory disease that may cause severe illness and life-threatening complications in some people. Influenza can lead to clinical symptoms varying from mild to moderate respiratory illness to severe complications, hospitalisation and in some cases, death. 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. Seasonal influenza is a vaccine-preventable disease which exerts an annual health burden across Europe of up to 70,000 deaths.
About CSL Seqirus
CSL Seqirus is part of CSL (ASX: CSL). As one of the largest influenza vaccine providers in the world, CSL 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, CSL Seqirus utilises egg, cell and adjuvant technologies to offer a broad portfolio of differentiated influenza vaccines in more than 20 countries around the world.
For more information about CSL Seqirus, visit CSL.com.
About CSL
CSL (ASX:CSL) (USOTC:CSLLY) is a global biotechnology company with a portfolio of 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 products to patients in more than 100 countries and employs 32,000 people. Our 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, 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.
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FLUAD® (Influenza Vaccine, Adjuvanted)
PATIENT MEDICATION INFORMATION5
What is FLUAD® (Influenza Vaccine, Adjuvanted)?
FLUAD® is a vaccine that helps protect people aged 65 years and older from the flu. Vaccination with this may not protect all people who receive the vaccine.
Who should not receive FLUAD®?
You should not receive FLUAD® if you have a history of severe allergic reactions (e.g., anaphylaxis) to any component of the vaccine, including egg protein, or to a previous influenza vaccine.
Before receiving FLUAD®, 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 any flu vaccine 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 FLUAD®?
• pain, tenderness, redness, itching, bruising, and/or swelling where the vaccine was given
• headache
• extreme tiredness
• muscle aches
• feeling unwell (malaise)
Additional side effects seen in children include:
• raised hardened area where the vaccine was given
• changes in eating habits/loss of appetite
• sleepiness
• irritability
• diarrhea
These are not all the possible side effects of FLUAD®.
You can ask your healthcare provider for more information and for advice about any side effects that concern you.
What do I do if I have side effects?
Report any severe or unusual side effects to your healthcare provider.
To report SUSPECTED ADVERSE REACTIONS, contact CSL Seqirus at
1-855-358-8966 or VAERS at 1-800-822-7967 or www.vaers.hhs.gov.
Before receiving any of this vaccine, please see the full US Prescribing Information for FLUAD®. You can ask your healthcare provider or pharmacist for information about FLUAD® that is written for healthcare professionals.
1 Imran, M. et al. Comparable Vaccine Effectiveness of Adjuvanted and High-Dose Influenza Vaccines in Preventing Test-Confirmed Influenza Outcomes, including Hospitalization, in Overall and High-Risk Older Adults: A Test-Negative Design Study During 2022–2023 and 2023–2024.
2 Madsen, K et al. A Public Health and Comparative Cost Analysis of Enhanced Influenza Vaccination in Adults Aged ≥ 65 years Compared to Current Programs Across the Nordic Region.
3 European Centre for Disease Prevention and Control (ECDC). Systematic review of the efficacy, effectiveness and safety of newer and enhanced seasonal influenza vaccines for the prevention of laboratory-confirmed influenza in individuals aged 18 years and over. Available online at https://www.ecdc.europa.eu/sites/default/files/documents/Systematic-review-update-enhanced-seasonal%20flu-vaccines-2024-rev-with-covers.pdfhttps://www.ecdc.europa.eu/sites/default/files/documents/Systematic-review-update-enhanced-seasonal%20flu-vaccines-2024-rev-with-covers.pdf. Accessed October 2025.
4 European Centre for Disease Prevention and Control (ECDC). Factsheet about seasonal influenza. Available online at https://www.ecdc.europa.eu/en/seasonal-influenza/facts/factsheet. Accessed October 2025.
5 FLUAD® Prescribing Information and product monograph available online at https://health-products.canada.ca/dpd-bdpp/info?lang=eng&code=84739. Access October 2025.