New Data Supports the Effectiveness of Adjuvanted Seasonal Influenza Vaccine in Reducing Influenza-Related Hospitalizations and Healthcare Costs in Older Adults

Seqirus, a global leader in influenza prevention and a business of CSL Limited (ASX:CSL), today announced new real-world evidence (RWE) supporting the relative effectiveness of FLUAD® (Influenza Vaccine, Adjuvanted), its adjuvanted trivalent vaccine (aTIV), compared with standard-dose, non-adjuvanted trivalent influenza vaccine (TIV) and standard-dose quadrivalent influenza vaccine (QIV) in reducing influenza-related outcomes over 18 influenza seasons in Italy. Additionally, two studies demonstrated the cost effectiveness of FLUAD® QUADRIVALENT (Influenza Vaccine, Adjuvanted), its adjuvanted quadrivalent seasonal influenza vaccine (aQIV) in Spain and France. These data were presented at the European Scientific Working Group on Influenza (ESWI) 8th Virtual Conference held from December 4-7, 2021.

An adjuvant, such as MF59®, is designed to help boost the immune response to influenza vaccination in adults aged 65 years and older, who are more susceptible to flu complications. Adjuvanted influenza vaccines are authorized for use in many national immunization programs around the world to help protect people against influenza.

“Age-related immune decline can make it harder for the body to mount a sufficient immune response to flu vaccination in people aged 65 and older, who currently account for an estimated 727 million people globally – a number expected to double by 2050,” said Gregg Sylvester, MD, Chief Medical Officer, Seqirus. “The data presented at ESWI 2021 provide new evidence for the adjuvanted influenza vaccines in this population.”

New data from an independent study highlighted the relative effectiveness of aTIV compared with TIV and QIV against all-cause or respiratory-related hospitalization in adults aged 65 and older across 18 consecutive influenza seasons in Italy (2001/02 to 2018/19). In this study, findings demonstrated that aTIV was associated with 12% lower risk of hospitalization and a 37% lower risk of respiratory-related hospitalizations compared with TIV and QIV.

A separate study presented at the conference utilized a decision tree model, which was calibrated to estimate influenza-related costs and benefits of aQIV and high-dose quadrivalent influenza vaccine (QIV-HD) in a one-year time span. Results suggest that the use of aQIV may lead to an increase in quality-adjusted life years and substantial cost savings in Spain.

“In Spain alone, nearly one fifth of the population is aged 65 and older as of 2020, and this percentage can be expected to grow in the coming years,” said Sergio Marquez-Pelaez, Pablo de Olavide University, Seville, and study-co-author. “The use of enhanced seasonal influenza vaccines, such as those that utilize an adjuvant, not only help to reduce influenza-related outpatient visits and hospitalizations in this population but may also reduce the economic and societal burden associated with increased outpatient medical encounters, as suggested by the data presented at ESWI.”

Researchers also presented a budget impact model analysis in France that concluded utilizing aQIV in place of QIVe over a three year period may result in increased vaccination costs of about €90.7M, but could yield potential savings totaling €66.3M from fewer influenza events and complications driven by avoidance of medical care visit costs, outpatient complication costs and inpatient complication costs. These findings are similar to the published models in the UK and Italy, evaluating cost effectiveness of adjuvanted quadrivalent influenza vaccine.

The World Health Organization (WHO) estimates that seasonal influenza may result in nearly 290,000 to 650,000 respiratory deaths each year. The WHO recommends annual vaccination as the most effective way to prevent influenza, especially for people at a higher risk of influenza complications such as individuals over 65 years of age.

Effectiveness of adjuvanted trivalent vaccine (aTIV) for influenza over 18 epidemic seasons
The relative effectiveness of aTIV compared to TIV/QIV against all-cause hospitalization or respiratory-related hospitalization in older adults (≥65 years) was determined in an independent study across 18 consecutive influenza seasons in Italy. A nested case-control analysis of older adults was conducted using an Italian data source of primary care called the Health Search Database. Conditional logistic regression was used to estimate outcomes in a cohort of 58,252 older adults vaccinated with aTIV or TIV/QIV.

The use of aTIV was associated with a 12% lower risk of hospitalization (OR=0.88; 95% CI: 0.80-0.98) and a 37% lower risk of respiratory-related hospitalizations (OR=0.63; 95% CI: 0.44-0.91) compared to TIV/QIV across 18 influenza seasons in Italy.

The study was subject to the typical limitations associated with retrospective cohort analyses. Observational studies have limitations including the potential for selection bias and residual confounding. Individual study limitations may include: retrospective analyses, a potential lack of laboratory confirmed influenza, and varying data sources.

An Economic Evaluation of Enhanced Influenza Vaccines for the Elderly in Spain. The Adjuvanted Quadrivalent Influenza Vaccine versus High-Dose Quadrivalent Influenza Vaccine
The authors evaluated the cost-effectiveness of aQIV compared with QIV-HD in older adults aged 65 and above in Spain using a decision-tree model with Spanish demography and costs extracted from Spanish and European published literature as well as Spanish tender prices for aQIV and QIV-HD.

Results suggest that vaccination with aQIV in older adults helped prevent 4,141 symptomatic influenza cases, 759 office visits, 441 hospitalizations, and 25 deaths annually, resulting in an increase of 211 quality-adjusted life years and substantial cost savings compared with QIV-HD. From payer and societal perspectives, about €63M and €64M savings, respectively, were estimated in the model.

Budget Impact Analysis of the MF59-Adjuvanted Quadrivalent Influenza Vaccine in the Older Adult French Population
Seqirus also presented an evaluation of the budget impact of a national immunization program in France based on the progressive use of aQIV instead of standard egg-based QIV (QIVe) or QIV-HD. The model forecasts influenza-related costs and benefits for the next 3 seasons, starting in 2021.

Over a 3-year period, it was estimated that 56,028 influenza cases, 13,449 medical care visits, 30,815 outpatient complications, 3,902 inpatient complications, and 745 influenza-associated deaths may be prevented by switching from QIVe to aQIV vaccinations. Results suggest that progressively transitioning from QIVe to aQIV could potentially result in increased vaccination costs of about €90.7M, with about €66.3M in savings from fewer influenza events and complications, driven by avoidance of medical care visit costs (€470K), outpatient complication costs (€788K), and inpatient complication costs (€23.2M).

Economic evaluations in health can be a very useful complement to the decision-making process, and the methodological approaches should be continually being refined and improved. Caution must be exercised in interpreting the results of economic evaluations performed in a given setting and in extrapolating to a different population, location, healthcare systems and resource use. It’s strongly suggested that economic evaluations should be performed on a regular basis to ensure that the results are valid and up-to-date, and consistent with payer’s views and priorities of the societies which are under research.