Can Concomitant Flu, PCV, and DTaP Vaccines Affect Febrile Seizure Risk?

During febrile seizures, babies fall unconscious and may convulse. Their eyes may roll back, and their limbs may twitch or become rigid.

However, febrile seizures lasting less than 15 minutes shouldn’t cause any long-term health problems, and they don’t necessarily mean that the child has epilepsy, according to the National Institute of Neurological Disorders and Stroke. Still, no parents want their children to experience febrile seizures.

Although the absolute risk of febrile seizures related to vaccinations is small, study results have shown that concomitant administration of some vaccines may increase that risk.

Before 2010, no study results in the United States showed an increased risk of febrile seizure after receiving the trivalent inactivated influenza vaccine. In Australia, however, a greater risk was linked with a flu vaccine manufactured by CSL Limited.

In observed cases, the febrile seizures tended to occur in the first 12 hours following vaccination. This association was also observed for the trivalent inactivated influenza vaccine made by Sanofi Pasteur for the 2010-2011 flu season.

Some stakeholders theorized that the 13-valent pneumococcal conjugate vaccine (PCV), which was introduced in 2010, might have had something to do with the increased risk. Therefore, researchers sought to determine whether vaccines administered on the same day as the flu vaccine could affect the risk of febrile seizures.

“We observed that children who received the influenza vaccine on the same day as a DTaP [diphtheria-tetanus-acellular-pertussis] vaccine were more likely to have a febrile seizure than children who had received either 1 of these vaccines without the other. This had not been studied before and was a new finding,” Jonathan Duffy, MD, MPH, of the CDC’s Immunization Safety Office, told Pharmacy Times. “We found that febrile seizures occurred very rarely among children who had received both vaccines on the same day, with no more than 30 febrile seizures per 100,000 children vaccinated.”

The take-home message for pharmacists and parents is that vaccines are critical to the child’s and other children’s health, and the benefits of vaccines greatly outweigh the risks of a potential febrile seizure.

In Dr. Duffy’s study, the risk of febrile seizure on the same day or the day after vaccination was examined for all routinely recommended vaccines in children aged 6 to 23 months over 5 flu seasons (2006-2007 to 2010-2011). The research team found 596 potential cases of febrile seizure out of nearly 2 million vaccinations, and febrile seizure was confirmed in 348 cases. Around half of the children had previously experienced a febrile seizure.

In medical visits post-seizure, an infection was found in 77% of the patients. Upper respiratory infection was the most common, followed by otitis media, viral infection not otherwise specified, urinary tract infections, and lower respiratory tract infections.

Dr. Duffy and his fellow researchers also found that the 7-valent PCV had an independent febrile seizure risk. The trivalent inactivated influenza vaccine had no independent risk, but there was an increased risk when it was administered with PCV or a DTaP-containing vaccine. Again, this risk was small.

“Parents should keep in mind that the vaccines recommended for children in the United States protect against serious infections that can sometimes require hospitalization or cause death,” Dr. Duffy said. “…The benefits of vaccination are much greater and longer lasting than the small risk of a child having a febrile seizure in the first few days after getting a vaccine.”

Dr. Duffy added that the Advisory Committee on Immunization Practices reviewed these results and didn’t see the need to change the recommended use for any of the vaccines.

“Influenza vaccine, when needed, should still be given at the same time as these other vaccines,” Dr. Duffy noted.