Influenza Vaccine Study in Older Adults Supports Flexible Vaccine Strategies for Health Systems and Long-Term Care Facilities

Older adults remain disproportionately vulnerable to severe influenza-related complications, hospitalizations, and death, making effective vaccination strategies a major priority for infection preventionists, long-term care facilities, and health care systems. A new large-scale real-world study involving more than 430,000 adults aged 65 years and older across 65 health care facilities found no significant difference in effectiveness between adjuvanted and high-dose influenza vaccines, reinforcing current Advisory Committee on Immunization Practices (ACIP) recommendations that both remain appropriate options for this high-risk population.

In this Q&A with Infection Control Today (ICT), Mendel Haag, PhD, senior director of the Center of Outcomes Research & Epidemiology in global medical affairs at CSL Seqirus, discusses the operational implications of the findings, ongoing challenges surrounding influenza vaccine uptake among older adults, the importance of real-world vaccine effectiveness research, and the role of health care providers in combating vaccine misinformation and hesitancy.

ICT: This study found no significant difference in effectiveness between adjuvanted and high-dose influenza vaccines in adults aged 65 years and older. From an infection prevention and public health perspective, how might these findings influence vaccine selection strategies within health care systems and long-term care facilities?

Mendel Haag, PhD: These findings reinforce the ability for health care systems and long-term care facilities to operationalize existing recommendations with greater confidence.

Given that adjuvanted and high-dose influenza vaccines are already recommended for adults aged 65 years and older, the demonstrated comparability in effectiveness supports their interchangeable use within vaccination programs.

In practice, this allows facilities to make procurement and implementation decisions based on factors such as supply availability, logistics, and cost, without concern that these choices would meaningfully affect expected protection in their populations.

ICT: Older adults account for the majority of influenza-related hospitalizations and deaths each year. What operational or educational challenges do infection preventionists still face when trying to improve influenza vaccination uptake among this population?

MH: Influenza vaccination coverage remains a challenge among older adults, even though this population remains at the highest risk for influenza-related hospitalization, severe complications, and death.

In the current environment, where people are exposed to a great deal of misinformation and disinformation, it is more important than ever for health care providers to make clear, routine vaccination recommendations to all eligible people. For older adults in particular, it remains important to clearly communicate that influenza is not a minor seasonal illness and that annual vaccination is the best available measure to help reduce serious outcomes. This communication needs to address reducing severe disease and hospitalizations, and position vaccination as a means of building wellness.

Operationally, improving uptake can depend on making vaccination as easy and routine as possible. That includes having an adequate supply of recommended vaccines for adults 65 years and older, offering vaccination early enough in the season, reducing access barriers such as transportation or scheduling challenges, and ensuring staff, residents, patients, and families receive consistent recommendations.

ICT: The researchers used a large cluster randomized crossover design across 65 facilities. What stands out to you about the study design itself, and do you think this type of real-world vaccine effectiveness research is valuable for infection prevention decision-making?

MH: Several aspects of this study design stand out as noteworthy, particularly the scale, which involved over 430,000 adults 65 years and older across 65 health care facilities.

What’s especially compelling is the randomization element of the design. By having facilities alternate, or in other terms, “cross-over,” weekly between administering adjuvanted and high-dose influenza vaccines, the study was intentionally designed to approximate individual randomization while still reflecting how vaccines are actually administered in routine clinical care.

In addition, using laboratory-confirmed influenza as the primary outcome provides a clear, objective assessment of infection across care settings based on routine testing practices.

By evaluating vaccine use at scale under routine conditions, this type of evidence helps strengthen confidence that observed effectiveness reflects how vaccination strategies perform in practice.

ICT: The study reinforces current ACIP recommendations that both adjuvanted and high-dose influenza vaccines are appropriate for adults 65 years and older. How important is that flexibility for health care organizations during vaccine procurement, supply shortages, or fluctuating influenza seasons?

MH: With comparable effectiveness between adjuvanted and high-dose influenza vaccines, both of which fall under ACIP’s preferential recommendation for adults aged 65 years and older, health care organizations have a greater ability to maintain vaccination programs without delaying immunization while waiting for one specific product.

Ultimately, having more than one recommended option helps protect access, sustain coverage, and support timely vaccination of a population at elevated risk for severe influenza outcomes.

ICT: Influenza prevention often competes with COVID-19 fatigue and vaccine hesitancy. What messaging approaches have you found most effective when discussing influenza vaccination with older adults, families, or health care workers?

MH: For older adults, grounding the conversation in personal risk is powerful. The data speaks for itself: between 70 to 85% of seasonal influenza-related deaths and 50–70% of influenza-related hospitalizations occur in people aged 65 and older. Framing vaccination not just as self-protection but as a way to preserve independence, avoid hospitalization, and maintain quality of life tends to resonate strongly with this group.

Health care providers and pharmacists remain the best messengers to discuss influenza vaccination with older adults and their families. These groups often find success by normalizing vaccination conversations as routine behavior, using strong, clear messaging that includes the fact that influenza can cause serious complications, that older adults remain at high risk of these complications, and that annual vaccination is the most important way to help protect against the illness.

CSL Seqirus is committed to supporting HCPs and pharmacists with the tools, data, and resources they need to have these conversations with confidence and impact.

ICT: Looking ahead, what additional research or surveillance data would infection prevention and IPC professionals like to see regarding influenza vaccine effectiveness, particularly in vulnerable older adult populations?

MH: Given the evolving nature of influenza viruses, ongoing surveillance and real-world evidence (RWE) remain essential to inform vaccination strategies and optimize protection for older adults and other vulnerable groups.

Ongoing RWE generation is important to extend our understanding of currently recommended influenza vaccines under different seasonal patterns of influenza circulation.