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A summary of presentations from the weekly Summit partner webinars

July 24, 2025 – The latest Summit Summary

H5N1, COVID-19 Epidemiology and COVID-19 Vaccine Updates

Lizette Durand, DVM, PhD, gave an update about H5N1; Ben Silk, PhD, gave an update about COVID-19; and Janell Routh, MD, MHS, gave an update about COVID-19 vaccination coverage and revised immunization schedules.

If you have any question regarding these presentations, please email info@izsummitpartners.org.

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Southern Hemisphere Flu Data

Karita Ambrose, PhD, gave an update about influenza trends in the Southern Hemisphere.

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Southern Hemisphere Flu Data– Karita Ambrose, PhD, Medical Affairs, Seqirus Vaccines
Current influenza trends in the Southern Hemisphere can help inform — but may not reliably predict — the flu season in the Northern Hemisphere, including the United States. Notably, Australia experienced a record-setting early start to its season, driven by low vaccination coverage, despite a good vaccine match to circulating strains.

Flu Surveillance in the Southern Hemisphere
Flu season typically spans April through September, occasionally extending into October or November.

The following data were reported by WHO:

    • Over 30,000 influenza cases reported in the Southern Hemisphere in the 2025 season.
      • 92% of tested viruses were influenza A; 7% were influenza B.
        • Among Influenza A:
          • 91% were H1N1
          • 8% were H3N2
        • All subtyped B viruses were from the B/Victoria lineage.
    • Australia and Argentina showed similar strain patterns, with influenza A (majority H1N1) dominating and B/Victoria strains present.

Unusual Early Activity in Australia
More than 46,000 confirmed cases occurred in Australia from January–March 2025 — the highest ever recorded in that period. Case numbers began rising again in early May, aligning more with typical seasonal patterns.

  • 2025 case numbers are about 4% lower than at the same point in 2024.
  • Pediatric populations are most affected, with the highest rates in 5- to 9-year-olds, followed by 0- to 4-year-olds.

Hospitalization Trends
The FluCAN Sentinel Hospital Network reported the following:

  • More than 6,000 admissions for severe acute respiratory infections; influenza was the leading cause, followed by RSV.
  • Influenza cases had a 50% increase; RSV had a 20% increase; COVID-19 admissions declined by 11%.
  • The influenza surge caused a burden to hospital systems: In Queensland, four hospitals paused elective surgeries; other states expressed concern but did not halt elective procedures.
  • A free flu vaccination program was introduced late in the season, but may have been too late to drive rates up.

Vaccination Rates in Australia
The national flu vaccination rate in Australia is 29% in 2025, nearly identical to 28% in 2024.

  • Vaccination by age group:
    • 6 m–5 years of age: 23.2%
    • 5–15 years of age: 13.9% coverage — lowest and most affected group
    • 15–50 years of age: 20%
    • 50–65 years of age: 31.3%
    • 65+ years of age: 59.7% — highest uptake
  • Free vaccines are offered under Australia’s National Immunisation Program to:
    • Pregnant women
    • Children 0–5 years of age
    • Adults 65+ years of age
    • Individuals 5–64 years of age with high-risk conditions

There is a vaccine match of over 98% of circulating strains are antigenically similar to 2025 vaccine components, which indicates a strong match.

Southern Hemisphere trends may offer useful context but do not reliably predict the U.S. influenza season due to:

  • Antigenic drift
  • Differences in timing and peaks
  • Egg adaptation in vaccine production

QUESTIONS & ANSWERS

Q: Will CDC be putting out guidance on when to stop giving the 2024–2025 COVID-19 vaccination? Some providers are wondering when to stop that relative to 2025–2026 being available.
Lauren Roper (CDC): I don’t know that we’ll have guidance on when to stop giving it. But for your awareness, there is a 2-month minimum interval. So, if people get it later in the summer, it may cause them to have to delay it a little bit in the fall. We’ll have to see if, with the new approvals from the FDA, that’s still the case.
Q [follow-up]: Some of the previous data show that even having the earlier version of the vaccine provides significant rise in titers that would be effective in helping to reduce your risk of infection, correct?
Lauren Roper (CDC): Correct. And the currently circulating variants are still JN.1 lineage and similar to the vaccine from last year.
Carolyn Bridges (Immunize.org): So, don’t hold off. If you are one of those people who is living in an area that’s seeing increases in activity, you should use the COVID-19 vaccine that you currently have available for someone who wants to be protected. And then, once the new ones become available, you would get vaccinated again at the minimum interval of 2 months.

Q: Does the CDC have any idea about vaccine availability around the country because there are obviously some folks who are waiting for the “next generation” — is there an access issue?
Janell Routh (CDC): We have not heard of any supply issues at this time.

Q: Are there any differences that you’re hearing about adults 65 and older having access to that second dose — the six-month dose? Are there any access problems that you’re aware of, particularly with Medicare?
Janell Routh (CDC): We have not heard of anything.

Q: Didn’t the vaccine expire at the end of June, or were expiration dates extended?
Carolyn Bridges (Immunize.org): Flu vaccines always expire at the end of June.
Lauren Roper (CDC): Novavax, specifically, expired earlier in the year; I’m not aware of any issues with expiration on the others.
Janell Routh (CDC): Yes, and Dr. Regensteiner (CDC) is confirming that, as well.

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Announcements
  • The next Summit weekly virtual meeting is August 14, 2025.
  • 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.

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