Flu Shots May Decrease Pediatric Influenza-Associated Encephalopathy and Acute Necrotizing Encephalopathy

While the U.S. Centers for Disease Control and Prevention (CDC) recently stated that Influenza-associated encephalopathy (IAE) is a rare, severe neurologic complication of influenza, all children are at risk for severe neurologic complications of flu.

This CDC conclusion, published in the Morbidity and Mortality Weekly Report (74(36);556–564), was validated during the 2024-2025 flu season, when 109 pediatric cases were identified. 

Approximately one-half of these children were previously healthy with no underlying medical conditions.

Thirty-seven of these IAE cases were subcategorized as acute necrotizing encephalopathy (ANE), a severe form of IAE characterized by rapid neurologic decline and a poor prognosis.

Overall, 19% of IAE patients died, and 41% of ANE patients died in this analysis.

The CDC states that IAE is a recognized complication of influenza, referring to neurologic syndromes triggered by influenza virus infection of the respiratory tract, which results in a dysregulated host inflammatory response and leads to varying degrees of brain dysfunction.

One of the most severe forms of IAE is ANE, a condition that disproportionately affects children and is characterized by rapid neurologic decline and neuroimaging with evidence of necrosis or hemorrhage involving the thalami; ANE has a poor prognosis and can result in lasting neurologic sequelae or death.

Since 2010, the CDC and the Advisory Committee on Immunization Practices have recommended annual influenza vaccination for all persons aged 6 months and older to prevent influenza illness and reduce the severity of influenza in children who do become ill, including a reduction in the occurrence of critical and life-threatening flu complications.

Influenza vaccination has also been found to reduce influenza-associated hospitalization and emergency department visits in children.

Yet, despite these known benefits, pediatric influenza vaccination coverage has declined in recent years, and only 16% of vaccine-eligible IAE patients in this analysis had received one of the approved 2024–25 influenza vaccines.

Furthermore, these researchers revealed that preadmission oseltamivir treatment among these IAE patients was low.

The CDC recommends that outpatients with suspected or confirmed influenza who are at high risk for influenza complications initiate influenza antiviral treatment as soon as possible after symptom onset. 

Whether influenza antiviral therapy affects the development or progression of IAE is unknown; however, one study demonstrated that oseltamivir treatment for influenza in outpatients aged 5–17 years was associated with a reduced risk of hospitalization with serious neuropsychiatric events, including neurological events such as seizures, altered mental status, and encephalitis.

In the future, the CDC plans to integrate surveillance for IAE and ANE into existing CDC-sponsored surveillance systems for the 2025–26 influenza season, aiming to better understand these severe and potentially preventable complications of influenza.