The Advisory Committee on Immunization Practices recommended that a seasonal influenza vaccine manufactured by CSL Biotherapies for the U.S. market not be used in children between the ages of 6 months and 8 years.
The company's trivalent influenza vaccine (TIV) sold under the trade name Afluria in the United States was associated with a large increase in the risk of fevers and febrile seizures in children in Australia and New Zealand. In April 2010, authorities in those two countries recommended that physicians suspend use of CSL's influenza vaccines in children aged 5 years and under. In response, the company voluntarily withdrew its vaccine from markets in the southern hemisphere.
In the northern hemisphere, CSL's influenza vaccines have been approved for use in Germany, the United Kingdom, and the United States. In June 2010, authorities in the United Kingdom recommended that physicians avoid using CSL's influenza vaccine in children aged 5 years and under.
In making their recommendation, members of the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) noted that there should be adequate supplies of seasonal influenza vaccine even in the absence of Afluria. Other manufacturers are expected to supply 145-150 million doses of the vaccine in the United States; the largest number of doses ever used in one flu season was 114 million.
During the course of the teleconference, representatives of Sanofi-Aventis, GlaxoSmithKline, Novartis, and MedImmune all said that they had adequate supplies of vaccine, and they were willing to increase production if necessary to compensate for the 6-12 million doses that CSL had been expected to provide.
According to the CDC's Dr. Tim Uyeki, CSL's vaccine was associated with a ninefold increase in the risk of febrile seizures, compared with other manufacturers' vaccines in children aged 6 months through 4 years in Australia.
The rate was nine per 1,000 doses in these children, compared with an expected rate of one per 1,000 doses. The rate of febrile seizures was especially high in children aged 3-4 years old given Fluvax Junior, one of CSL's two versions of this year's TIV. The rate in those children was 15 per 1,000 doses.
Febrile seizures occurred an average of 7.2 hours after the child received a dose of vaccine, with a range of 5.9-8.4 hours. Dr. Uyeki said that no explanation for the increased risk of fever and febrile seizures has been identified.
Although there was no apparent increase in febrile seizures in children aged 5-8 years, children in that age group did experience an increase in the incidence of fever. Sixteen percent of children in that age group experienced a fever following a dose of a CSL flu vaccine, compared with 9% of children receiving another manufacturer's vaccine.
ACIP members voted to include children aged 5-8 years in their recommendation in order to increase the simplicity and consistency of the public health message. Other ACIP recommendations regarding flu vaccination in children, both for the seasonal TIV and for pandemic influenza A(H1N1), involve children age 6 months to 8 years, and most members believed it would be confusing to have this new recommendation cover children age 6 months to 5 years.
They did agree, however, that children aged 5-8 years could receive the CSL vaccine if they were at especially high risk from influenza and if no other vaccine was available.
Several committee members voiced concern about providers who may already have placed orders for the CSL vaccine. Since most vaccine from other manufacturers has already been allocated, they worried that it would be too late for some clinicians to change their orders. In response, a representative from the American Medical Association recommended that providers visit the AMA's Influenza Vaccine Availability Tracking System (IVATS) at http://www.preventinfluenza.org/ivats
In related news, the CDC reported Aug. 4 that they've observed outbreaks of seasonal influenza A(H3N2) in two nonbordering counties in Iowa, along with sporadic cases of influenza 2009 H1N1 A and B in 11 other states.
The agency reminded physicians to consider influenza as a possible diagnosis in individuals with respiratory illnesses even though influenza is not often seen in the summer. Clinicians also were advised not to rely on the rapid influenza diagnostic test because of its moderate sensitivity and an increased chance of false positives during times when overall influenza prevalence is low.
Disclosures: While several members of ACIP disclosed that they had relationships with vaccine manufacturers, only members with no such conflicts of interest were permitted to vote.