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    Acellular pertussis component of combo vaccine has low risk of febrile seizure

    Coming at a time when more parents are questioning the safety of the pertussis vaccine and putting their children at risk of contracting whooping cough, a new study finds that the acellular pertussis component of a combined vaccine has minimal risk of febrile seizures and a lower risk of epilepsy in early life.

    Aware that whole-cell pertussis vaccine is associated with fever and a greater risk of febrile seizures, investigators evaluating whether the same risk applies to the acellular pertussis component of a combined diphtheria-tetanus toxoid-acellular pertussis–inactivated poliovirus–Haemophilus influenzae type b (DTaP-IPV-Hib) vaccine found the absolute risk to be less than 4 per 100,000 vaccinations but also found that there is a significantly higher risk of febrile seizures on the day of administration of the first and second doses in the 3-dose series.

    Researchers examined data from 378,834 children born between 2003 and 2008 in Denmark, where acellular pertussis vaccine has been included in the combined vaccine since September 2002, and found that it was associated with a 4- to 6-fold greater risk of febrile seizure on the day of administration of the initial dose at age 3 months and of the second dose at 5 months. A similar association was not found for the third dose at 12 months. A booster is recommended at 5 years. (In the United States, the recommended DTaP schedule is at ages 2, 4, and 6 months, with a fourth dose at 15 to 18 months and a booster at 4 to 6 years.)

    The risk of febrile seizures was not elevated during the week after vaccination, the study found, and compared with unvaccinated children, those receiving the vaccine had a lower risk of epilepsy from 3 to 15 months and a similar risk later in life.

    The researchers acknowledge that because the DTaP-IPV-Hib vaccine was given as a combined vaccine throughout the study period, some uncertainty remains about which components of the vaccine caused febrile seizures on the day of vaccination.

    The findings come at a time when parental concern has shifted from preventing disease transmission to vaccine safety, causing many to forego immunization for their children, according to a separate study that found a strong association between parental vaccine refusal and the risk of pertussis infection in children.

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