Young children face a “significantly elevated” risk of seizures following COVID-19 vaccination, according to a new study.
In a preprint published on medRxiv, researchers from the U.S. Food and Drug Administration (FDA) found the incidence of febrile seizures was 2.5 times higher among children within a day of receiving Moderna’s COVID-19 vaccine compared with the same children 8 to 63 days after vaccination.
There was also a higher risk for febrile seizures 0 to 1 day after children received the Pfizer-BioNTech vaccine than in the 8 to 63-day window following vaccination, but that elevated risk was not statistically significant, researchers said.
The researchers evaluated children aged 2-5 years for febrile seizures 0-1 days following COVID-19 vaccination and 8-63 days after vaccination to compare the risk of seizures. The study period started on June 17, 2022, when emergency use authorization for COVID-19 vaccines occurred in this age group, and the smaller risk interval was used because it’s more likely that a vaccine caused the seizure if it happened the day of or the day after vaccination.
There were 288,754 Pfizer-BioNTech vaccinations and 192,540 Moderna vaccinations given among 163,733 and 110,126 children, respectively.
In a primary analysis, researchers observed 88 cases of febrile seizures following vaccination with Pfizer. Of the 88 cases, 7 occurred the day after vaccination, and 81 occurred during the 8—to 63-day control interval.
Sixty-seven cases of febrile seizures occurred following vaccination with Moderna’s COVID-19 vaccine. Of the 67 cases, 10 occurred during the two-day window, and 57 were observed during the longer window.
In a primary meta-analysis, researchers found that seizures occurred more than twice as often on the day of or following vaccination with Moderna compared to the control interval. The incidence of seizures following Pfizer vaccination was elevated but not statistically significant, researchers wrote.
Using a longer risk interval of 0 to 7 days, researchers found 103 cases of febrile seizures and 135 cases of seizures/convulsions following vaccination with Pfizer’s COVID-19 vaccine, of which 22 cases of febrile seizures and 32 cases of seizures/convulsions occurred during the risk interval.
There were 78 cases of febrile seizures and 106 cases of seizures/convulsions observed following vaccination with Moderna’s COVID-19 vaccine, of which 21 cases of febrile seizures and 28 cases of seizures/convulsions were observed during the risk interval.
A febrile seizure is a convulsion in a child usually triggered by a high fever. Fever is a common side effect of COVID-19 vaccines and occurred in 19% of children aged 2 to 3 during Pfizer’s clinical trial following a second dose.
The study was initiated after a safety signal was found among children aged 2 to 4 following Pfizer’s COVID-19 vaccine and among children aged 2 to 5 following Moderna.
“Based on the current body of scientific evidence, the safety profile of the monovalent mRNA vaccines remains favorable for use in young children,” the researchers concluded.
It is well-established that young children are not at risk of experiencing severe COVID-19, nor are they often symptomatic. Yet, US regulatory agencies like the FDA are still recommending COVID-19 vaccines despite the risk of experiencing a fever or, worse, a seizure.