Although vaccines have helped save countless lives over the decades, many parents avoid or delay getting their children vaccinated for fear of side effects. Now a new study confirms that when young children are vaccinated, the risk of a febrile seizure is low, and the benefits seem to outweigh the risks.
The study comes from Jonathan Duffy, MD, MPH and colleagues at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. The researchers published their results online June 6th in the journal Pediatrics. During the 2010-2011 influenza season, researchers had identified an increased risk of febrile seizure (FS) when children were given the influenza vaccine around the same time as the pneumonia vaccine. The researchers in the current study set out to determine if there was a risk for children receiving different vaccines close together.
For their study, the researchers analyzed data from 1,915,108 vaccinations. The data came from the Vaccine Safety Datalink, a partnership between the CDC and health care organizations. The researchers called the day of the vaccination and the next day the risk interval period, in which an inactive vaccine can cause febrile seizure, and days 14 to 20 after the vaccination the control period, in which neither live or inactive vaccines should cause febrile seizure. The researchers skipped days 2 to 14 because they already know the risk of febrile seizure from live vaccines during this time is 1 in 3,000.
The study defined febrile seizure as a temperature higher than 100.4 degrees Fahrenheit, excluding patients with a history of febrile seizure, head infection, or metabolic issues. In the influenza seasons between 2006 and 2011, the researchers found 333 confirmed cases of febrile seizure in children aged 6 to 23 months. 103 of the cases occurred during the risk period, within a day of their vaccination, and 230 occurred during the control period, between 14 and 20 days after vaccination. Febrile seizures in the control period were caused by infections such as urinary tract, respiratory tract, ear, and viral.
The researchers looked at whether the children had received their pneumonia vaccine (PCV) along with an influenza vaccine (IIV3) or a diptheria/tetanus/acellular pertussis (DTaP) vaccine, or whether they received the vaccines separately. They found that when children received two vaccines together, there was a greater risk of febrile seizure, at 30 for every 100,000 children.
The data also showed that there was no increased risk of febrile seizure when children received the flu shot on its own, but the pneumonia vaccine did have an increased risk of febrile seizure on its own. However, the risk for febrile seizure can vary year to year because each season’s flu shot has a different formula than the previous year.
The study did have some limitations, such as not studying every possible combination of vaccines and having a relatively low number of febrile seizure cases to analyze. However, the study does suggest a small risk of febrile seizure with vaccine combinations.
Despite the risk, the study authors point out that the risk of febrile seizure after vaccination is small. They believe the benefits of the vaccines do outweigh the possible risks for children. Children can be fussy when faced with a painful vaccine at the doctor’s office, so it may be beneficial to get all the relevant vaccines at once. That way, doctors can be sure that their young patients got all the vaccines they need at that stage in their development. Even if a parent plans to bring their child back for the missed vaccine, this is not always the case, and the doctor may not notice later that the one vaccine was missed. In addition, the time before the child comes back for their missed vaccine means a longer time they remain unvaccinated and vulnerable to illness. The flu, pneumonia, and other diseases pose a risk to children’s health that outweighs the possible risk of febrile seizure, from which most children successfully recover. Not only that, since about twenty percent of children who are hospitalized for influenza experience a febrile seizure, not getting the flu shot can actually increase the risk of febrile seizure.
According to the CDC, every year an average of 20,000 children under age 5 end up in the hospital from flu complications, and one flu season could see 140 deaths for children. Children under the age of two can face severe influenza complications, especially those with chronic health conditions like asthma, diabetes, and brain or nervous system disorders. The CDC recommends children over the age of six months receive annual flu vaccinations.