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The U.S. Food and Drug Administration (FDA) wants flu vaccines to carry a warning that the shots can cause febrile seizures in young children.
The agency’s Center for Biologics Evaluation and Research (CBER) last week sent notices to several vaccine makers — including Sanofi, AstraZeneca, GSK and CSL Seqirus — asking them to add the warning.
CBER cited two postmarketing observational studies it conducted, which found that children between the ages of 6 months and 4 years faced a higher risk of febrile seizure in the day following vaccination.
The FDA proposed this wording for the vaccine labels:
“In two separate postmarketing observational studies, an increased risk of febrile seizures was observed during the first day following vaccination with standard dose trivalent (2024-2025) and quadrivalent (2023-2024) influenza vaccines in children 6 months through 4 years of age.”
The warning would be added to the labels of AstraZeneca’s FluMist, GSK’s Fluarix, ID Biomedical’s FluLaval, Sanofi Pasteur’s Fluzone, and Sequiris’ Afluria and Flucelvax vaccines.
The vaccine makers have 30 days to either agree to the proposed label update, propose changes or submit a rebuttal.
A spokesperson for Sanofi told Fierce Pharma that febrile seizures have occurred only in a “limited subset of patients” and that the company already includes information about such seizures in Fluzone’s label.
GSK told Fierce Pharma the company is reviewing the FDA’s request and that the company is “confident” in the “safety and efficacy profile” of its flu shots.
‘Any seizure is bad, period’
Febrile seizures are convulsions most often caused by fevers triggered by infections related to common childhood illnesses. The seizures typically occur in children 6 months to 5 years old when they have a fever over 100.4 F.
Most febrile seizures last less than 15 minutes and are not life-threatening. According to Medpage Today, they “do not cause any permanent harm and do not have any lasting effects.”
Brian Hooker, Ph.D., chief scientific officer for Children’s Health Defense (CHD), disagreed. “Any seizure is bad, period,” he said.
“‘Mild’ febrile seizures can double a child’s chance of an epilepsy diagnosis and ‘complex’ febrile seizures — lasting more than 15 minutes — can increase that risk up to 10 times,” Hooker said.
Karl Jablonowski, Ph.D., CHD’s senior research scientist, said, “The entire construct supporting the permissibility of febrile seizures post-vaccination hinges on one idea, that they are harmless.”
Jablonowski said some studies, including a 2023 review in Frontiers in Cell and Developmental Biology, indicate this may not be the case. The review showed that “febrile seizures occurring during neurodevelopment … may ‘ultimately lead to disease,’” he said.
The review “specifically highlights ADHD [attention-deficit/hyperactivity disorder], epilepsy and cognitive decline in adulthood,” he said.
Hooker suggested that claims that febrile seizures are harmless help normalize an injury that may cause broader harm to children, particularly those with other health conditions.
“It is sickening how vaccine reactions are minimized and normalized at the hands of Big Pharma,” Hooker said. “Too many children are being harmed — the rate of seizures in autistic people can be as high as 20% — with the damage swept under the rug.”
Several types of vaccines linked to higher rate of febrile seizures
CBER evaluated the flu vaccines for two cold and flu seasons between 2023 and 2025. The agency analyzed insurance company data to compare the incidence of febrile seizures in children 6 months to 4 years in the first day following vaccination, with the incidence of such seizures eight to 63 days post-vaccination.
According to CBER, the data indicated an estimated excess rate of 21.2 febrile seizures per million standard-dose quadrivalent flu vaccinations and 44.2 extra seizures following administration of trivalent vaccines.
A 2012 study of children ages 6 months to 2 years found an increased risk of febrile seizures in the 24 hours following the co-administration of an inactivated flu vaccine and the 13-valent pneumococcal conjugate (PCV13, or pneumonia) vaccine or the diphtheria, tetanus, acellular pertussis (DTaP) vaccine.
Dr. Meryl Nass, an internal medicine physician and founder of Door to Freedom, agreed that the flu shots pose a risk of febrile seizures. But, she said, other vaccines — including the measles-mumps-rubella (MMR) vaccine — pose an even greater risk.
Last year, the Advisory Committee on Immunization Practices (ACIP), which advises the Centers for Disease Control and Prevention (CDC) on vaccine policy, voted to no longer recommend the MMRV (measles-mumps-rubella-varicella) vaccine for children under age 4.
ACIP’s vote followed a presentation containing evidence of an increased risk of febrile seizures following the MMRV vaccine.
In a 2024 study published in JAMA Network Open, FDA researchers detected a safety signal for seizures in young children following mRNA COVID-19 vaccination. Most of the seizures were febrile.
A safety signal is a sign that an adverse event may be caused by vaccination, but further research is required to verify a link.
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In a preprint published earlier in 2024, FDA researchers found that children ages 2-5 who received the COVID-19 mRNA vaccine faced an increased risk of febrile seizures immediately following vaccination.
Nass questioned CBER’s use of observational studies to draw its conclusions.
“What we need are some prospective, active surveillance studies to get real numbers on the rates of febrile seizures and other problems in young children.” She said these problems often don’t get detected in retrospective medical record studies.
CBER’s notice to the makers of flu vaccines came just days after the U.S. Department of Health and Human Services made sweeping changes to the childhood vaccination schedule, reducing the number of recommended vaccines for all children from 17 to 11.
As part of those changes, flu vaccines are no longer recommended for all children. Instead, the CDC now recommends shared clinical decision-making between physicians and parents.
Last year, ACIP voted to stop recommending flu vaccines that contain thimerosal, a mercury-based preservative linked to neurodevelopmental disorders.
A Cleveland Clinic study of 53,402 adults last year found that people who received a flu shot during last year’s cold and flu season had a 27% higher chance of getting the flu.
Related articles in The Defender- FDA Finds mRNA COVID Vaccines May Cause Seizures in Toddlers
- Kids Ages 2-5 Had Higher Rate of Convulsions After mRNA COVID Shots
- FDA Finds ‘Safety Signal’ of Seizures in Children 2-5 After COVID mRNA Vaccines
- Breaking: HHS Makes Sweeping Changes to Childhood Vaccine Schedule
- ACIP Votes to Recommend Kids Don’t Get MMRV Vaccine Until Age 4, Delays Vote on Hep B for Newborns
- ‘Deeply Concerning’: This Year’s Flu Shots Led to 27% Higher Risk of Flu
