Febrile seizure risk and vaccines

A recent study¹ found that although vaccines are associated with an increased potential risk of febrile seizure in young children, the overall risk is small, suggesting that following the currently recommended immunization schedule may be the optimal approach in managing appropriate vaccination of young children of immunization age.

The childhood immunization schedule in the United States is put forth by the Centers for Disease Control and Prevention (CDC) based upon recommendations made by the Advisory Committee on Immunization Practices (ACIP). According to the current recommendations, influenza vaccine should be administered annually to everyone aged 6 months or older; children should receive 5 doses of diphtheria, tetanus, and acellular pertussis (DTaP) vaccine, which are recommended to be given at ages 2, 4, and 6 months, between 15 to 18 months, and between 4 to 6 years; and children should receive 4 doses of pneumococcal conjugate vaccine (PCV), which are recommended to be given at ages 2, 4, and 6 months, and between 12 to 15 months.

One of the long-standing issues with administering these vaccines is that they can cause fever, which in young children can lead to febrile seizures. The question returns to many wary practitioners and concerned parents as to whether the benefits of a timely administration of recommended vaccines outweigh the risk of developing febrile seizure.

“These vaccines prevent infections that can sometimes be severe or life threatening. The benefits of timely vaccination are likely much greater than the small risk of febrile seizure. Febrile seizures are relatively benign and do not cause lasting harm. Influenza vaccine, when needed, should still be given at the same time as these other vaccines,” says Jonathan Duffy, MD, MPH, Immunization Safety Office, CDC, Atlanta, Georgia, and lead author of the recent vaccination study.

In the study, Duffy and colleagues used the Vaccine Safety Datalink to assess whether certain vaccines if given alone or in combination with other vaccines can be associated with febrile seizures. Data examined included the risk of febrile seizure 0 to 1 day postvaccination for all routinely recommended vaccines (influenza, PVC, and DTaP) among children aged 6 to 23 months during a period encompassing 5 influenza seasons (2006-2007 through 2010-2011). It was found that only PVC vaccine was associated with an increased rate of febrile seizure when given alone, but whereas influenza vaccine had no independent risk, the risk for febrile seizure was increased when given together with PVC or DTaP.

The study also found that the concomitant administration of influenza, PVC, and DTaP vaccines can lead to febrile seizures at a rate of up to 30 in 100,000 children immunized. For the average pediatrician, who may annually see 1000 children aged younger than 5 years, including 3 to 500 aged between 6 and 24 months, one could expect to see at most 1 child who experiences a febrile seizure every 5 to 10 years because of administration of these vaccines together in the first 2 years of life. That would be a risk of 1 febrile seizure per pediatric practice every 5 to 10 years.

According to Duffy, upon review of the results of this study as well as others concerning fever and febrile seizures following childhood vaccines, the ACIP decided that the small risk of febrile seizure following PCV vaccine and the vaccine combinations studied were outweighed by the benefits of the vaccines. These vaccines can prevent serious and life-threatening infections, Duffy says, and the ACIP continues to recommend that these vaccines be given and that they can be given together when needed.

“Febrile seizures are known to occur at a low rate following certain vaccines, however, there are currently no evidence-based methods recommended to prevent febrile seizures following vaccination. The potential benefit of vaccination to prevent febrile seizure over longer periods is less readily apparent than the short-term risk of febrile seizure in the first few days immediately after vaccination. Over the long-term, vaccination might reduce the risk of febrile seizure, although additional study would be needed to quantify this for each type of vaccine. We hope the results of our current study will help doctors and parents make informed decisions about vaccination for individual children,” Duffy says.

More information about the ACIP and current vaccine recommendations can be found online at: www.cdc.gov/vaccines/acip/index.html.

REFERENCE

1. Duffy J, Weintraub E, Hambidge SJ, et al; Vaccine Safety Datalink. Febrile seizure risk after vaccination in children 6 to 23 months. Pediatrics. 2016;138(1):e20160320.