The introduction of COVID-19 vaccines marked a significant public health achievement, prompting widespread discussion about their effects. This article addresses concerns regarding whether COVID-19 vaccines can cause seizures, examining available scientific evidence from large-scale studies and global monitoring systems to provide a clear overview.
Understanding Seizures and Vaccine Reactions
A seizure is a temporary disruption of normal brain activity, manifesting as involuntary movements, altered consciousness, or changes in sensation. These events result from sudden, uncontrolled electrical disturbances in the brain. All vaccines can cause side effects as the immune system responds. Common, mild reactions include pain at the injection site, fatigue, and headache.
Vaccination can also cause generalized symptoms like fever, part of the normal immune response. Most vaccine side effects are temporary and not serious. Global monitoring systems, such as the Vaccine Adverse Event Reporting System (VAERS) in the United States, collect reports from healthcare professionals and the public to identify potential safety concerns.
COVID-19 Vaccines and Seizure Data
Extensive research and surveillance data examine the relationship between COVID-19 vaccines and seizures. A comprehensive meta-analysis of six placebo-controlled clinical trials (over 118,000 individuals) found no significant association between SARS-CoV-2 vaccination and new-onset seizures. This suggests new seizures do not occur more frequently in vaccinated individuals than in placebo recipients.
Large-scale studies and health authorities consistently report that seizures following COVID-19 vaccination are extremely rare. A nationwide observational study in Mexico, analyzing over 80 million vaccine doses, found an incidence rate of 0.64 seizures per million doses across all vaccine types. The U.S. Centers for Disease Control and Prevention (CDC) estimates approximately 3.19 seizures per 100,000 people per year following COVID-19 vaccination, typically occurring within four weeks and often as new-onset events. While this rate is higher than that for influenza vaccines (estimated at 0.090 per 100,000 people per year), it remains very low. A report to a surveillance system does not automatically establish a causal link; it only indicates an event occurred after vaccination.
How Seizures Might Relate to Vaccination
While broad data does not support direct causation, certain physiological responses to vaccination could indirectly influence seizure activity in specific circumstances. Fever, a common side effect of many vaccines, including COVID-19 vaccines, can sometimes trigger febrile seizures, particularly in young children. Febrile seizures are convulsions caused by a rapid increase in body temperature and are a known, albeit rare, occurrence following various childhood immunizations, not just COVID-19 vaccines.
The immune response to vaccination involves the release of inflammatory molecules, which can contribute to symptoms like fever. In rare instances, this inflammatory response or associated sleep disruptions might increase the likelihood of a seizure in susceptible individuals. Individuals with pre-existing neurological conditions, such as epilepsy, may coincidentally experience a seizure around vaccination. Some studies report a small percentage of people with epilepsy experiencing a temporary increase in seizure frequency post-vaccination; these events are often transient and do not suggest a worsening of the underlying condition. The risk of experiencing seizures from a COVID-19 infection is significantly higher than any potential risk from the vaccine.
Guidance for Vaccine Recipients
Anyone experiencing seizure-like symptoms after a COVID-19 vaccine should seek immediate medical attention. Healthcare providers can evaluate symptoms and determine the appropriate course of action. Report any adverse events following vaccination to relevant health authorities. In the United States, anyone can submit a report to the Vaccine Adverse Event Reporting System (VAERS), and healthcare professionals are encouraged to report all clinically significant events.
Public health organizations and medical experts affirm the safety and effectiveness of COVID-19 vaccines. Major health organizations agree that vaccination benefits, including protection against severe illness, hospitalization, and death from COVID-19, far outweigh the extremely rare potential risks. People with pre-existing conditions, including epilepsy, are generally advised to get vaccinated after consulting with their healthcare provider.