Febrile Seizures: Scary but Benign

“I think it’s very important to tell parents that, yes, your child is getting a vaccine, and they can have fever that goes up rapidly or down rapidly…It is a simple, short seizure associated with fever, and it is not having any long-term consequences."

Sharon Nachman, MD, Chief of Pediatric Infectious Diseases, Stony Brook Children’s Hospital

“To parents and caregivers, watching their child experience a febrile seizure is no doubt a frightening experience, even though these seizures are almost always harmless to children.”Adam J. Ratner, MD, MPH, editor of the Red Book: 2024-2027 Report of the Committee on Infectious Diseases

A seizure (convulsion) is one of the scariest medical conditions to witness. Febrile seizures are, however, relatively common in children. Thankfully, they are usually harmless and rarely caused by vaccines.

Nonetheless, on January 9, 2026, the US Food and Drug Administration (FDA) requested that the manufacturers of six influenza vaccines include an updated warning about the risk of febrile seizures in young children. The FDA’s “request” prompted me to write this week’s Germ Gems post in which I provide an overview of febrile seizures.

Let fever do its job. Defined as an elevation of the body’s temperature set-point, usually above 38C or 100.4F, fever is with rare exception a normal and evolutionarily beneficial response to infection. As such, there is virtually never a reason to treat a fever. Treatment of the underlying cause of fever, on the other hand, is what’s needed.

This admonition not to treat a fever is in sharp contrast to hyperthermia—an elevation of body temperature caused most commonly by external heat exposure. Hyperthermia can be life-threatening and requires urgent lowering of body temperature whereas fever does not.

Febrile seizures. Febrile seizures are a type of seizure that can occur when an otherwise healthy child (6 months to 5 years of age) develops a fever. They are relatively common in young children and can be caused by anything that causes a fever, such as the common cold, the flu, or an ear infection. (“Fact Checked: Febrile Seizures Do Not Cause Brain Damage or Long-Term Health Effects,” American Academy of Pediatrics, December 12, 2025.) They are usually harmless and do not cause long-term health issues. (Meningitis and encephalitis are not causes of febrile seizures.)

A vaccine-induced febrile seizure is exceedingly rare. As Dr. Adam J. Ratner said, “The important thing to remember is that most pediatricians will not see a case of vaccine-induced seizure over the course of their careers—that’s how rare they are.”

According to the American Academy of Pediatrics (AAP), “roughly 3 to 5% of children will experience a febrile seizure during their childhood.” But the odds of a child experiencing a vaccine-related seizure are lower than that. “Febrile seizures occur in 1 in 1100 to 1400 children immunized with a first dose of Measles, Mumps, Rubella, Varicella (MMRV) vaccine at 12 through 23 months of age and in 1 in 2500 to 3000 children immunized with a first does of Measles, Mumps, Rubella (MMR) and varicella vaccines administered at the same time in separate injections.”

Febrile seizure treatment. As a rule, children who seize within the context of having a fever should be seen by a pediatrician trained to determine the cause of the fever and treat the cause of the fever rather than the seizure. The physician may determine that a lumbar puncture (LP) is necessary to rule out meningitis or encephalitis. All decisions about invasive procedures such as LPs and the administration of antibiotics in children with febrile seizures require the expertise of a pediatrician. (Seams, J., O’Leary, S., “Moving the Field Forward to Safely Do Less with Febrile Neonates,” Journal of American Medical Association, December 8, 2025).

Why it matters: vaccines save lives. Whether the FDA needed to coax the influenza vaccine manufacturers to highlight febrile seizures as a side effect of their vaccines is hard for me to gauge. Febrile seizures have been known to be a potential, albeit usually benign, development with several other vaccines. The fact that the recommendation to add the warning came from a RFK Jr.-led advisory committee isn’t surprising, however, as Mr. Kennedy and his cronies are known to emphasize the dangers rather than the benefits of vaccination.

It is important to emphasize that vaccines help prevent infections that can lead to febrile seizures. As the AAP stated: “Distorting or overstating the risks of febrile seizures following vaccination can cause undue anxiety in parents and caregivers and contribute to vaccine hesitancy” thereby “increasing the risk of children developing fevers that can trigger febrile seizures.”

Perhaps the best way to see this “warning” is in a positive light—as a way of keeping parents informed. As Dr. Nachman said: “I think the [vaccine safety] warning is very helpful, because I think it should be part of what we tell parents. ‘Your child will make an immune response to this vaccine. Part of your immune response is to have fever, and with the sudden increase, her (sic) drop in fever. Your child could have a very brief febrile seizure, which actually has no long-term sequalae. Be warned and don’t be worried.”(Nachman, S., Parkinson, J., “Vaccines and Febrile Seizures: What Everyone Should Know,” Contagion Live, February 1, 2026).