Flu-Associated Pediatric Deaths, Pediatric Flu-Associated Encephalopathy, and more

["Morbidity and Mortality Weekly Report \(MMWR\) \(CDC\)" <no-reply@xxxxxxxxxxxxxxxxxxxx>]

Pediatric Flu Deaths

September 25, 2025

In this Issue

Flu-associated encephalopathy, children Flu-associated deaths, children	2025 flu vaccine interim effectiveness, Southern Hemisphere

WEEKLY REPORT

Pediatric Influenza-Associated Encephalopathy and Acute Necrotizing Encephalopathy

Health departments and clinicians reported 109 influenza-associated encephalopathy (IAE) cases to CDC during the 2024-25 flu season, of which 37 (34%) were categorized as one of the most severe forms of the disease, acute necrotizing encephalopathy (ANE). Children with IAE had serious illness. Most children with IAE (74%) were admitted to an intensive care unit; one in five (19%) died. The median age of children with IAE was 5 years. More than half (55%) of children with IAE were previously healthy, and only 16% of those who were eligible had received a 2024-25 flu vaccine.

• Influenza-Associated Pediatric Deaths

  The 2024–25 flu season was marked by the highest number of pediatric deaths during a regular (non-pandemic) flu season since flu-associated deaths in children became nationally notifiable in 2004. As of September 13, 2025, 280 flu-associated pediatric deaths have been reported to CDC for the 2024-25 flu season.

• Interim Effectiveness Estimates of 2025 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Outpatient and Hospitalized Illness

  2025 seasonal flu vaccines reduced flu-associated outpatient visits and hospitalization by an estimated one half in eight Southern Hemisphere countries. Vaccine effectiveness against flu–associated hospitalizations was approximately 51% among young children, 52% among people with underlying medical conditions, and 38% among older adults.

READ THE WEEKLY REPORTS

PDF of this issue (link)

Questions about this MMWR? Contact us at mmwrq@xxxxxxx

MOST READ THIS WEEK

• Clinical Recommendation for the Use of Injectable Lenacapavir as HIV Preexposure Prophylaxis — United States, 2025 
• Prevalence and Early Identification of Autism Spectrum Disorder Among Children Aged 4 and 8 Years — Autism and Developmental Disabilities Monitoring Network, 16 Sites, United States, 2022 
• Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2025–26 Influenza Season 
• CDC Clinical Practice Guideline for Prescribing Opioids for Pain — United States, 2022 
• Suicide Rates by Industry and Occupation — National Vital Statistics System, United States, 2021 

In Case You Missed It

Use of Clesrovimab for Prevention of Severe Respiratory Syncytial Virus–Associated Lower Respiratory Tract Infections in Infants: Recommendations of the Advisory Committee on Immunization Practices — United States, 2025

CDC recommends clesrovimab for infants younger than 8 months of age born during or entering their first respiratory syncytial virus (RSV) season if the mother did not receive RSV vaccine during pregnancy, the mother’s RSV vaccination status is unknown, or the infant was born less than 14 days after maternal RSV vaccination. In clinical trials, clesrovimab was about 91% effective against RSV-associated hospitalization and about 60% effective against severe RSV. Clesrovimab is the second long-acting RSV antibody to be recommended for infants (nirsevimab was the first).

Respiratory Syncytial Virus Immunization Coverage Among Infants Through Receipt of Nirsevimab Monoclonal Antibody or Maternal Vaccination — United States, October 2023–March 2024

An analysis of data from 36 state and local immunization information systems found that 29% of infants born during October 2023–March 2024 received protection against respiratory syncytial virus (RSV). Infant RSV protection through infant or maternal immunization ranged by state from an estimated 11% to 53%.

U.S. Centers for Disease Control and Prevention

1-800-CDC-INFO (800-232-4636)   TTY: 888-232-6348
Questions or Problems  |