A new preprint study led by the U.S. Food and Drug Administration (FDA) has detected a potential “safety signal” for seizures and convulsions in young children after receiving the monovalent Pfizer or Moderna mRNA Covid-19 vaccines.
Researchers observed the condition in children ages 2-4 for the Pfizer vaccine, and ages 2-5 for the Moderna vaccine.
The total number of cases was 72, with over 50% meeting the definition for febrile seizures.
The median time between vaccination and seizures or convulsions was two days, with 32% occurring the day of or the day after vaccination. All seizures and convulsions took place within seven days of vaccination.
The signal emerged through near real-time surveillance of more than 4 million vaccinated children.
The researchers of the preprint study cautioned that the results “should be interpreted carefully given study limitations.”
The study also identified a myocarditis/pericarditis safety signal in mostly male children 12-17 years old.
However, since each of these conditions were a “known adverse outcome,” according to the researchers, they did not conduct any further follow-up.
Data for the study were collected through health claims records from CVS Health, Optum and Carelon Research, which participate in the FDA’s Center for Biologics Evaluation and Research, and supplemented with data from state and local immunization information systems databases.
The study covered reports through January, February or March of this year — as little as 6 months after the approval of vaccinations for younger children.
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