ATLANTA – A small but significantly increased risk for febrile seizures within a day of vaccination was seen among children aged 12–23 months who received Fluzone and Prevnar 13 concomitantly in a real-time analysis of data from a large managed care database that includes 2.2 million children.
The preliminary data from the Vaccine Safety Datalink (VSD), presented at the meeting suggest an attributable risk of 61 per 100,000 cases, or 1 excess febrile seizure for every 1,640 vaccinees who receive both vaccines simultaneously. There was no increased risk for the two vaccines given separately, nor for children younger or older than 12–23 months.
For comparison, the excess risk of febrile seizures for the measles-mumps-rubella-varicella vaccine, compared with MMR and varicella given separately, is 43 per 100,000 doses, noted Dr. Grace Lee of Harvard Pilgrim Health Care Institute, Boston.
Dr. Michael Marcy, a member of the Advisory Committee on Immunization Practices, commented that the average pediatrician sees about 200 newborns a year, so the excess risk translates to about one additional febrile seizure every 8 years. That's on top of the 48–90 febrile seizures per 1,600 children that already occur among children for a variety of reasons, including influenza. “It would get lost,” he said in an interview.
Indeed, the ACIP liaison from the American Academy of Family Physicians, Dr. Douglas Campos-Outcalt, said in an interview that “it's a pretty small risk. It certainly was an increased risk, but the absolute risk wasn't very high. You have to put the whole thing in context. Febrile seizures are a concern to parents, but they aren't life-threatening events. I think it's worth counseling parents, but vaccine risks are pretty low.”
Dr. David Kimberlin, co-liaison to ACIP from the American Academy of Pediatrics, said that “the data are extremely preliminary. Until we know more, there should be no changes to the use of influenza vaccine in pediatrics in the United States.”
Concern about Fluzone – the only influenza vaccine recommended for use for the 2010–2011 flu season in infants and children 6–23 months of age – arose from a data mining signal from the passive Vaccine Adverse Events Reporting System. Prior to that, a report from Australia suggested a statistically increased risk for febrile seizures within a day of receipt of another brand of flu vaccine that has since been pulled from the market worldwide.
The VSD will continue to monitor this until the end of the influenza season and will also look for possible roles of other concomitant vaccines. An ACIP working group will consider additional information on febrile seizures following vaccination, said Dr. Frank DeStefano of the CDC's Immunization Safety Office.
In a statement, Pfizer spokesman Curtis Allen said, “In addition to Pfizer's routine safety surveillance, we have conducted a comprehensive evaluation of our Prevnar 13 safety data, including results from clinical trials and our post-marketing safety database and, at this time, we have not observed a change in the safety profile with respect to febrile seizures. Our safety evaluation is ongoing and we will continue to work closely with the CDC and FDA to evaluate the CDC data, which are preliminary and require further investigation.”