Vaccines have significantly reduced infectious diseases, but public discussions sometimes arise regarding their safety, including concerns about seizures in children. While serious adverse events following vaccination are uncommon, temporary reactions can occur. This article provides information on the relationship between vaccines and seizures.
Vaccines and Seizure Occurrence
Vaccines can rarely be associated with seizures in children, primarily due to fever. These events are uncommon, and the risk varies depending on the specific vaccine. For example, measles-containing vaccines, such as the measles, mumps, rubella (MMR) vaccine, have a small increased risk for febrile seizures occurring 5 to 12 days after the first dose. The combined measles, mumps, rubella, and varicella (MMRV) vaccine carries a slightly higher, though still small, risk compared to separate MMR and varicella injections for the first dose.
Inactivated vaccines, like the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine, can also rarely be associated with febrile seizures, usually within 24 to 48 hours following administration. When given alongside other vaccines, such as the influenza vaccine and pneumococcal conjugate vaccine (PCV13), the risk of a febrile seizure can be slightly increased. The overall risk of a seizure following vaccination is very low, far less common than seizures caused by the natural infections vaccines prevent.
Understanding Febrile Seizures
Febrile seizures are the most common type of seizure in childhood, affecting approximately 2% to 5% of all children, typically between 6 months and 5 or 6 years of age. These seizures are triggered by a fever, defined as a body temperature above 38.4°C (101.1°F), and are not directly caused by the vaccine components themselves. The fever following vaccination is an expected immune response as the body learns to fight off future infections.
A febrile seizure often appears as a brief, generalized convulsion, involving stiffening and jerking movements of the limbs, and typically lasts less than 15 minutes. These seizures are generally benign and do not cause long-term brain damage or developmental problems. The mechanism involves the fever itself, which can make a child’s brain more susceptible to a seizure in some individuals.
Identifying Seizure Causes
It is important to distinguish between febrile seizures triggered by vaccine-induced fever and seizures occurring coincidentally after vaccination due to an underlying neurological condition. Many seizures in children are not related to vaccines and can stem from various causes, including infections, metabolic imbalances, or genetic predispositions. For instance, a small number of children with specific genetic conditions, such as Dravet syndrome, may experience their first seizure around the time of vaccination.
In these cases, the vaccine-induced fever acts as a trigger that unmasks an underlying genetic or structural brain disorder, rather than causing the condition itself. Studies indicate that the majority of children diagnosed with new-onset epilepsy following vaccination have an identifiable genetic or structural neurological disorder. Therefore, a medical evaluation is important if a child experiences a seizure, regardless of recent vaccination, to determine the underlying cause and ensure appropriate care.
Ensuring Vaccine Safety
Robust systems are in place globally to monitor vaccine safety. In the United States, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) co-manage the Vaccine Adverse Event Reporting System (VAERS). VAERS acts as an early warning system, collecting reports of potential adverse events from anyone, including parents, healthcare providers, and manufacturers.
While VAERS reports do not prove causation, they help identify patterns that warrant further investigation. Signals from VAERS are then often analyzed using more extensive systems like the Vaccine Safety Datalink (VSD), which utilizes electronic health records for active surveillance. This comprehensive approach ensures continuous monitoring of vaccine safety, confirming that the benefits of vaccination in preventing serious diseases far outweigh the rare risks of adverse events like febrile seizures.