High-Severity Influenza Season in the US Brings Increased Hospitalizations

Strategic Insights -

A severe influenza season in the US, characterized by the co-circulation of two types of influenza viruses, resulted in a high number of hospitalizations. According to preliminary data, the cumulative influenza-associated hospitalization rate surpassed all previous end-of-season rates since the 2010-11 season. The highest hospitalization rates were seen among individuals aged 75 years and older.

Key Takeaways:

  • The 2024-25 influenza season in the US was a high-severity season with co-circulation of influenza A(H1N1)pdm09 and A(H3N2) viruses.
  • The cumulative influenza-associated hospitalization rate was 127.1 per 100,000 population, exceeding all previous end-of-season rates since the 2010-11 season.
  • Hospitalization rates were 1.8 to 2.8 times higher than median historical rates during the same period.
  • Among hospitalized patients, 32.4% had received an influenza vaccine, and 84.8% received antiviral treatment.
  • The majority of patients (89.1%) had one or more underlying medical conditions, and 16.8% were admitted to an ICU.

Statistics:

  • Cumulative influenza-associated hospitalization rate: 127.1 per 100,000 population
  • Highest hospitalization rates among individuals aged 75 years and older (598.8 per 100,000 population)
  • Hospitalization rates were 1.8 to 2.8 times higher than median historical rates
  • 32.4% of hospitalized patients had received an influenza vaccine
  • 84.8% of hospitalized patients received antiviral treatment
  • 89.1% of patients had one or more underlying medical conditions
  • 16.8% of patients were admitted to an ICU
  • Deaths in hospital: 3.0%

Sources:

  • Medical Letter on the CDC & FDA. Recent Studies from National Center for Immunization and Respiratory Diseases Add New Data to Influenza Vaccines (Influenza-associated Hospitalizations During a High Severity Season - Influenza Hospitalization Surveillance Network, United States, 2024-25 Influenza Season). Medical Letter on the CDC & FDA, October 26, 2025; p 639.
  • Mmwr-morbidity and Mortality Weekly Report. Influenza-associated Hospitalizations During a High Severity Season - Influenza Hospitalization Surveillance Network, United States, 2024-25 Influenza Season. Mmwr-morbidity and Mortality Weekly Report, 2025;74(34):529-537.