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A summary of presentations from the weekly Summit partner webinars

December 18, 2025 – The latest Summit Summary

Lancet Study Update – Federico Martinón-Torres, MD, PhD, Head of Paediatrics, Director of Translational Paediatrics and Infectious Diseases at the Hospital Clinico Universitario de Santiago (Spain), Associate Professor of Paediatrics at the University of Santiago and Academician of the Royal Academy of Medicine and Surgery of Galacia

Federico Martinón-Torres, MD, PhD, gave an update about the FLUNITY-HD study of influenza vaccine effectiveness.

Results and learnings from a large individually randomized influenza vaccine effectiveness study: FLUNITY-HD – Federico Martinón-Torres, MD, PhD
The FLUNITY-HD study is the largest study performed to date on vaccine effectiveness, as far as Dr. Martinón-Torres knows. It was a prespecified pooled analysis of two methodologically harmonized, pragmatic, individually randomized trials (GalFlu and DanFlu-2) that assessed the relative vaccine effectiveness (rVE) of high-dose influenza vaccine compared with the standard dose influenza vaccine against severe disease outcomes. Results were recently published in The Lancet.

Study Methods
The study included almost 500K individually randomized people — in Denmark and Spain — to receive either high-dose or standard-dose influenza vaccines. Ultimately, owing to subtle differences in the populations in the two included studies, the limitations of real-life conditions, and dosing history, only subjects 65 to 79 years of age were included.

Endpoints & Results
As part of specific effectiveness results, Dr. Martinón-Torres mentioned that the results give the highest estimate for the most specific endpoints and move towards the lowest estimates for the least specific endpoints; he noted that, while causality cannot be inferred, this does present the biological possibility.

  • Primary endpoint
    • Hospitalization for influenza or pneumonia
      • Result: The use of high dose influenza vaccine over the standard dose influenza vaccine had an rVE of 8.8%, meaning that the high dose vaccine provides an additional 8.8% vaccine effectiveness.
  • Secondary endpoints
    • Hospitalization for any cardio-respiratory disease
      • Result: rVE 6.3%. The weight of this measure comes mostly from the rate of hospitalization for heart failure (rVE: 21.3%).
    • Laboratory-confirmed influenza hospitalization
      • Result: rVE 31.9%.
    • All-cause hospitalization
      • Result: rVE 2.2%
    • All-cause mortality
      • Result: rVE 1.2%
    • Hospitalization for influenza
      • Result: rVE 39.6% (one-sided p value NA)
    • Hospitalization for pneumonia
      • Result: rVE 2.3% (one-sided p value NA)

Strengths & Limitations

  • Strengths
    • Large sample size
    • Power to detect differences for a strong endpoint
    • Consistency across systems and regions
    • Possibility to answer critical public health questions
  • Limitations
    • Open-label study relying on routine health care (potential for real-life imprecision, including the factor of two countries represented in the study populations)

Local & Regional Implications
The pragmatic approach of the study has demonstrated the feasibility of conducting rigorous clinical research within public health, allowing for rapid decision-making for the local and regional populations. The research model is scalable, replicable, and is now being used for other studies (e.g., RSV and COVID).

QUESTIONS & ANSWERS

Q:In your data with the FLUNITY study, the hospitalization rate for myocardial infarction was not significant: What’s your speculation on that number? We know that influenza vaccine prevents acute myocardial infarctions in people with cardiovascular disease — do you think it’s because the standard dose, the comparator, was just so good already, or what was the reason for that?
Federico Martinón-Torres (HCUS): That’s a very good question, and as you can imagine, we have struggled with that. We tried to go into more detail in this more recent study published in Circulation, but that is what we observed. I agree with [you that] the standard dose influenza vaccines may be good enough for that endpoint, and the added benefit of the high-dose influenza vaccine is not that big for that particular endpoint, while for the hospitalization due to cardiac insufficiency it is important, with an rVE of 20%, which also surprised us. This [no difference in hospitalization rate for MI] was consistent across not only FLUNITY, but in the separate studies, where we did not see that signal. For us, the most plausible explanation is precisely that there is no added benefit in that specific endpoint. And we could say something similar when we look at the results in the FLUNITY and we compare the high-risk groups, or those with, say, one or more comorbidities and those studies without comorbidities, where the estimates for the rVE are the same, which could be perceived as something negative, but the other way of interpreting it is that you are converting high-risk people into healthy people in terms of the risks of the outcomes of influenza by the use of the high dose vaccine. It’s interesting, and of course, these types of trials do not allow you to state causality or further biological explanations beyond the speculative part. But with almost half a million people, what is clear is that the signal is there, and what we have not been able to observe […] and you need to go above half a million to further replicate that. And what we found is what it is, and I think that the number and the design and the randomization gives validity to the obtained results.

Q: The same observation was made with stroke — that there didn’t seem to be a significant betterment due to the high dose versus standard dose — and I guess it would be the same argument?
Federico Martinón-Torres (HCUS): Yes, there were a lot of exploratory endpoints, and we include stroke and other composite neurovascular endpoints, but we were not able to reach any significant result for any of them.

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EXCITE Extension Program: H5N1 Update – Jackie Wilkins, PhD, EFNEP Project Director and Tina Horn, H5N1 EXCITE National Project Team Lead, State Dairy Program Coordinator, Clemson University

Jackie Wilkens, PhD, and Tina Horn gave an update about EXCITE H5N1 information and resources.

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EXCITE Extension Program H5N1 Update – Jackie Wilkins, PhD
EXCITE is funded via interagency agreement between the Extension Foundation and the Centers for Disease Control and Prevention (CDC) and the National Institute of Food and Agriculture (NIFA) and provides messaging and teaching and engagement about immunization.

H5N1 Strain & Concerns
H5N1 is a strain of influenza A that primarily affects birds.

  • The strain has spread to many wild mammals.
  • The first (novel) bovine case was confirmed in March 2025, and high levels of virus were shed in milk.
  • Human concerns include splashing of milk during farm work and recombination of H5N1 with other viruses in swine or humans.

EXCITE Focus
Through a merger of extension efforts, EXCITE defined key objectives for stakeholders to address H5N1 concerns

  • Cooperative Extension Dairy Agents
    • Increase knowledge/understanding of H5N1 and behavior change communication skills.
  • Dairy Producers
    • Increase knowledge/understanding of H5N1 and potential transference and impacts on human and animal health.
    • Adopt prevention practices on farms to reduce H5N1 risk to humans and animals.

Pilot States
EXCITE has identified and received funding for five H5N1 Pilot States. Each state has a specific approach to communication and education.

  • California
    • 6 State-wide Webinars with follow-on email communications
    • Needs assessments for support (may include pilot vaccine partnerships, rural mobile health clinics, etc.)
    • Fact sheets in English and Spanish
    • Survey about dairy producer perceptions of the outbreak and vaccines. (It was noted that some hesitation about vaccine delivery may be related to whether vaccination is offered on- or off-farm — and/or the perception of the importance of biosecurity [88% of respondents indicated their belief that biosecurity doesn’t work], among other things.)
  • Michigan
    • Agents have reached 20 farms in Michigan for PPE use and HPAI transmission training, including PPE supply distribution.
      • Education (training sessions)
      • Distribution of personal protective equipment (PPE)
      • Development/implementation of focus groups, including identifying interest in future webinar topics.
        • Four pilot focus groups, for topics such as barriers, motivators, and misunderstanding about PPE use, have been held.
  • Texas
    • Workshops across the state, incorporating H5N1 into existing programs about biosecurity
    • Schematics about the spread across barns, farms, counties, states, and the nation
  • Utah
    • The state is using the spring dairy show, county fairs, and dairy conference attendance to talk with producers and farm workers, including displaying a diorama/scavenger hunt to identify the dairy dozen and helping youth understand their impact
    • On-farm visits to 20 farms, reaching 32K lactating cows
    • Biosecurity signs at every dairy farm in the state
  • Idaho
    • The state is focusing on immunization education and vaccination clinics, along with farm safety education. They have needed an evolving strategy because the University of Idaho has stopped work or funding on some work. They are focusing their communication on dairy producers and middle managers with a focus on biosecurity programs for producers and extension educators.

EXCITE Extension Program H5N1 Update (Part 2) – Tina Horn
The first case of highly pathogenic avian influenza (HPAI) in dairy cows was confirmed in March 2025; since then, 1,086 herds have had a confirmed case, as of this meeting date, despite a recent period of 30 to 60 days with no new cases. Further, following a lull, cases in poultry have been ticking up during the fall of 2025, leading to growing concerns about the threat to human health.

  • There have been 71 cases, including 2 deaths, in humans attributed to this H5N1 virus.
  • Dairy producers and farm workers are at highest risk of exposure and play a critical role in reducing risk of spread and spill over to humans.

Risks to Farms, Animals, and Humans

  • Threats to farm sustainability
  • Concerns for animal health and welfare
  • Human infections and occupational risks
  • Widespread infection in the human population and risk of human-to-human transition
  • Greater human health crisis

Key Vectors

  • Raw milk: EXCITE is contacting states that allow the sale of raw milk to provide education.
  • Wildlife: Spread by wildlife may cause people to question the effectiveness of biosecurity.

Resources from EXCITE
EXCITE provides a one-stop shop for science-based H5N1 knowledge and resources: https://h5n1.extension.org/.

  • Materials
    • One-page Briefs
    • Posters and Banners
    • Fact Sheets
    • Social Media Posts
    • Booklets in English and Spanish
  • Events and Opportunities
    • H5N1 Monthly Update Meetings (and Archived Recordings/Slides)

QUESTIONS & ANSWERS

Q:Is there an opportunity here to message and promote seasonal flu vaccine, recognizing it doesn’t protect against H5 but to prevent humans from acting as mixing vessels, or just in general as a great public health intervention that people should still also be protected against seasonal flu?
Jackie Wilkins (EXCITE): There absolutely is an opportunity to message that, and we already include that in some of the information that we provide. We also have another initiative through EXCITE where we’ve just hired 30 health agents across the regions, with four or five positions within each of the regions, focused on adult immunization education. Similar types of resources are being created for that, and we’re trying to intermingle everyone’s knowledge about the resources across both initiatives. We’ll have findings related to the projects we presented today, which finish in February, and we’ll have more information then.

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Seasonal Influenza Update – Alicia Budd, MPH, Influenza Division, Centers for Disease Control and Prevention

Alicia Budd, MPH, gave an update about seasonal influenza.

Influenza Activity Update – Alicia Budd, MPH
Through the weekend of December 6, there is an increase in influenza activity across the country, with some areas seeing steeper increases than others. Increases are occurring in all age groups — the season started most clearly with kids and has now spread to adults. Levels are similar to last year without the rises earlier in the season reported from other countries.

Circulating Viruses
This year, there are four A H3N2 viruses and some H1 and B activity.

  • H1: These viruses are split between two subclades, but they all look similar epigenetically to the cell grown vaccine reference virus.
  • H3: These viruses are split between a variety of subclades, with the majority (89%) in subclade K, and only 9% are similar epigenetically to the cell grown vaccine reference virus.
    • Subclade K is a new and rapidly emerging subclade of the seasonal influenza A H3N2 viruses, and the majority of H3 viruses tested at CDC this year have been subclade K. It has 10 mutations in the surface protein hemagglutinin, so it’s considered antigenically drifted. The effect of these mutations on vaccine effectiveness is unknown.
  • B Victoria: These viruses, which are currently circulating at low levels, are split between a variety of subclades, but almost 90% are similar epigenetically to the cell grown vaccine reference virus.

Vaccine Protection
The vaccine continues to reduce overall community spread of flu and at least one study showed that our current vaccines do provide some subclade K protection for children and adults against flu-associated hospitalizations.

  • Although it’s not easy to predict vaccine effectiveness against drifted viruses, previous seasons have indicated that there can be substantial protection.
  • Even though we’re classifying the current rate as low severity, it still represents millions of illnesses, at least 30K hospitalizations, and 1,200 deaths.

H5 Update
There has been, in November 2025 in Washington state, another human case of highly pathological H5 that resulted in death.

  • The individual was infected with H5N5, which is different than the prior 70 human cases and different from what has been seen in cattle, which is H5N1.
  • The individual did have backyard mixed poultry on their property, and there was H5 identified in the county of residence and other counties in the state, and that is where it is thought the infection was acquired.

QUESTIONS & ANSWERS

There were no questions for this section.

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Coronavirus and Other Respiratory Viruses – Benjamin J. Silk, PhD, MPH, Coronavirus and Other Respiratory Viruses Division, National Center for Immunization and Respiratory Diseases

Ben Silk, PhD, MPH, gave an update about COVID-19 and other respiratory viruses.

Coronavirus and Other Respiratory Viruses – Benjamin J. Silk, PhD, MPH
The United States is at a historically low level of COVID activity. Percent positivity for the last two years has been lower during the winter wave as compared with the summer wave.

Genomic Surveillance Data for SARS-CoV-2
There is an increasing trend of the variant XFG. All variants in the NOWCAST estimates are from the JN1 lineage and are covered in the 2025-2026 vaccine, so good coverage is expected this year.

  • There have been wastewater detections of another variant (BA.3.3.2) that has more than 50 mutations compared to JN1 (BA.2.86). There have been detections in clinical specimens in Europe, Australia, and Africa. In recent weeks, the number of countries reporting this variant has been increasing.

COVID-19-Associated Data
There is nothing surprising in the laboratory detections data for COVID-19-associated hospitalizations.

  • In older adults, hospital admissions are highest for those age 85 and older.
  • In children, hospital admissions are highest for infants under six months old, making them a priority for immunization and protection through maternal immunization.

Mortality data shows weekly counts of deaths that are on a downward slope over the years.

RSV-Associated Data
The laboratory detection data show that RSV percent positivity is lower than previous recent seasons. The slower start to the season and slope of the trend line suggest that the peak might be lower or the season might be drawn out, or both.

  • RSV-associated hospitalization rates are lower compared to past seasons.
    • By age group, children under 4 years of age have the highest rates of hospitalizations; the next highest group is adults over 65.
  • Data show that there was a sizable impact on hospitalization rates due to RSV prevention products, just looking at maternal vaccination plus monoclonal antibodies.
    • Uptake seems to be about 10% better this year than last, so there is cause for cautious optimism for declines in RSV-associated hospitalizations in babies.

QUESTIONS & ANSWERS

Q:Have you seen any increases in maternal vaccination, or is it still strongly favoring monoclonal antibody administration?
Ben Silk (NCIRD): Yes, I have some of those data from the National Immunization Survey. There’s a dashboard on the CDC webpage called RespVaxView. The numbers I have are combined maternal vaccination and uptake of monoclonal antibodies, so I don’t have it broken out. I can say that most of the numbers I’m about to give you are monoclonal antibodies, not maternal vaccination. But, this year, we’re seeing about 40% of babies with reported protection against RSV through either combined maternal vaccination or antibodies; and compared to this time last year, that’s about 10% more, when it was 30% around this time. So that is some good news, it seems, so far.

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Announcements
  • Save the date for the 2026 National Adult and Influenza Immunization Summit in-person meeting: May 19 – 21, 2026 at the Crowne Plaza Atlanta Perimeter at Ravinia in Atlanta, GA.
    • The meeting page (https://www.izsummitpartners.org/2026-naiis/) will open for registration in early 2026.
    • Recommendations for items for the agenda for this meeting are welcome, by email to NAIIS.
    • Nominations for the Immunization Champion Awards (the Immunization Neighborhood Champion and the Laura Scott Flu Award) are welcome, and there will be a scientific poster session that will be open to submissions.
  • The 2026 NAIIS Weekly Webinar Zoom link (https://us06web.zoom.us/j/85431630748?pwd=MFbTnlM6HBGI8Ulb6FAaW7ra2lF8vt.1) will be updated via email announcement, so please watch for that to update your calendars.

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