Vaccine Update: What to Expect for the 2025-2026 Influenza Season

Using data from the influenza season in the Southern Hemisphere (in Argentina, Australia, Brazil, Chile, New Zealand, Paraguay, South Africa and Uruguay) from April-September 2025, the Centers for Disease Control and Prevention has published a report on the effectiveness of the 2025-2026 influenza vaccine. Influenza vaccine reduced influenza-associated outpatient visits and hospitalizations. The adjusted vaccine effectiveness rate for the prevention of outpatient visits for influenza-like illness (ILI) was 50.4%. The adjusted vaccine effectiveness rate for the prevention of hospitalization for all severe acute respiratory infections (SARI) was 49.7%. Of patients with ILI, only 21.3% had received influenza vaccine. Of those hospitalized with SARI, 15.5% were vaccinated for influenza. Influenza A was the most identified virus in both outpatient and hospitalized patients and was present in 82.4% of people with ILI and 94.9% of those with SARI. Influenza A(H1N1)pdm09 was the most prevalent variant, at 39.9% and 58.7% of ILI and SARI cases, respectively.¹ It is anticipated that protection from influenza vaccination in the Northern Hemisphere for the present 2025-2026 influenza season will be similar.

The 2024-2025 influenza season was more lethal for children than past years. Last season had the highest number of pediatric deaths reported at 280 in the United States since child deaths became nationally notifiable in 2004, except for the 2009-10 influenza A(H1N1) pandemic year. Approximately 50% of children who died from influenza in 2024-2025 had an underlying medical condition, and 89% were not fully vaccinated. Of those deaths, 240 (86%) were from influenza A and 38 (14%) were from influenza B.² Hospitalizations began to peak in January 2025 with an absolute peak during the week beginning Feb. 8. Of pediatric patients hospitalized for influenza, 48% were <5 years of age.³ During the 2024-2025 influenza season, 49.2% of children nationally were vaccinated against influenza, which was lower than the previous year at 53.4%.⁴ In Missouri, 44% of children were vaccinated against influenza⁵ and in Kansas, 49.8%.⁶

Already, influenza activity is being seen as of October 2025 with 90 cases of influenza A and 135 cases of influenza B detected in Missouri.⁵ The week of Oct. 13, three influenza A cases were detected at Children’s Mercy Kansas City. The bottom line is that influenza vaccines continue to protect children from ILI and hospitalization with SARI, as evidenced by their effectiveness during the recent influenza season in the Southern Hemisphere. The national percentage of children vaccinated continues to be <50%, and in Missouri the rate is lower than the national average. Last year was a deadly year for children with influenza illness, especially those with underlying health conditions, and even these children had less than ideal rates of influenza vaccination. As we begin to see the start of this year’s influenza season, it is important to strongly recommend influenza vaccines to all children older than 6 months of age and especially to children who are medically fragile with underlying health conditions. Children younger than age 5 are also more likely to require hospitalization due to influenza and require particular attention when recommending influenza vaccination.

References:

1. Rudd T. CDC report hints at the effectiveness of this year’s flu shot. Medpagetoday.com. Published September 26, 2025. Accessed October 17, 2025. https://www.medpagetoday.com/infectiousdisease/uritheflu/117670
2. Reinhart K, Huang S, Kniss K, Reed C, Budd A. Influenza-associated pediatric deaths — United States, 2024–25 influenza season. MMWR Morb Mortal Wkly Rep. 2025;74:565-569. doi:15585/mmwr.mm7436a2
3. AAP Research. Thousands of children hospitalized with RSV, flu, COVID in 2024-’25. American Academy of Pediatrics. Published July 1, 2025. Accessed October 27, 2025. https://publications.aap.org/aapnews/news/32427/Thousands-of-children-hospitalized-with-RSV-flu
4. Weekly US influenza surveillance report: key updates for week 17, ending April 26, 2025. FluView. Published May 2, 2025. Accessed May 5, 2025. https://www.cdc.gov/fluview/surveillance/2025-week-17.html
5. Missouri weekly influenza surveillance report: 2025-2026 influenza season. Missouri Department of Health and Senior Services. Accessed October 27, 2025. https://health.mo.gov/living/healthcondiseases/communicable/influenza/dashboard.php
6. Data dashboard. Immunize Kansas Coalition. Accessed October 27, 2025. https://www.immunizekansascoalition.org/datadash.asp