Aug 5, 2010 (CIDRAP News) – Because of reports of increased fever and seizures in Australian and New Zealand children, the US government's Advisory Committee on Immunization Practices (ACIP) recommended today that a seasonal influenza vaccine made by CSL Ltd. should generally not be used in children from 6 months through 8 years old this fall and winter.
The committee qualified its recommendation by saying the vaccine, called Afluria, could be used in children ages 5 through 8 who are at high risk for flu complications if no other vaccine is immediately available.
This provision was based on reports that adverse reactions have been less common in those children than in younger ones, and it also reflected concern that providers who have ordered CSL vaccine for use in children could find themselves in a tight spot if they can't use it.
The general sense of the teleconference meeting was that the recommendation will not cause any big disruptions in the vaccine supply.
Wendy Keitel, MD, chair of the ACIP flu vaccine working group, said, "The total number of doses if we completely remove the CSL doses at this moment is about 145 million at minimum to about 150 million doses across the country. The most we've distributed in a single season has been about 114 million, so we are significantly higher than that, even without adding in the CSL doses."
Flu vaccine makers have said they expect to produce a total of about 170 million doses for the US market this season. Last week CSL officials estimated they would produce up to 12 million doses for use in the United States.
At today's meeting, an official with Merck, which distributes Afluria in the United States, said CSL has decided not to distribute the vaccine in multidose vials. He said that will reduce the supply by about 5 million doses, leaving 6 million to 7 million doses packaged singly.
Tim Uyeki, MD, of the Influenza Division at the Centers for Disease Control and Prevention (CDC), summarized the data on the mysterious increases in fever and febrile convulsions seen in children who have received the CSL vaccine this year in Australia and New Zealand. The increased adverse reactions prompted Australian health officials to suspend vaccination of all children under age 5 on Apr 23, and New Zealand followed suit on Apr 26, he noted.
One study showed that the risk of fever was about 6.5 times higher in children under 5 years who received the CSL vaccine than in those who received another seasonal vaccine (Solvay's Influvac), Uyeki reported. Another study, which compared the CSL vaccine with a different vaccine, found the risk of fever was 8 to 10 times greater with the CSL product, he said.
Investigators also have found that the CSL vaccine was associated with a substantially higher risk of febrile seizures in children 6 months through 4 years old, compared with other vaccines. The overall rate of seizure was about 9 per 1,000 doses administered, or about 9 times higher than expected, Uyeki reported. For other vaccines used, the rate of febrile seizures in the same age-group was 0 per 1,000 doses, he said.
For children 5 through 8 years old, postmarketing surveillance has indicated increased reports of fever this year compared with the past thee flu seasons in Australia, though this finding "is subject to reporting biases," Uyeki reported.
Also, a 2009 study found that the rate of postimmunization fever in children 5 through 8 years was 16% for the CSL vaccine, versus 9% for another vaccine, he said.
Australia gave providers the go-ahead to resume use of seasonal flu vaccines other than the CSL product in small children (6 months through 4 years) on Jul 30, Uyeki reported. He said the United Kingdom, where CSL flu vaccines also are sold, has likewise halted their use in children younger than 5 years.
Uyeki and Keitel said investigators have been unable to find any explanation for the increased fever and febrile convulsions in children who received the CSL vaccine. There has been no evidence of endotoxin contamination, failure to inactivate the virus, or the presence of whole viruses, Keitel said.
She said the flu vaccine working group debated a number of options concerning the CSL vaccine. The majority opinion was that Afluria should not be used in children 6 months through 8 years, with the exception for 5- through 8-year-olds at risk for complications when there is no alternative.
"The main point being that we have other options for the control of influenza in the US," she said.
For the sake of clear messaging, a minority of working group members favored dropping the exception for older children and simply recommending against use of the vaccine in any children through age 8, Keitel added.
Much of the ensuing discussion focused on the strength of the signal of increased risk for ages 5 through 8 and on potential effects on the availability of vaccine for children. Some ACIP members and liaison members also voiced concern that the recommendation would be confusing and favored dropping the exception for older kids.
A CSL representative told the committee the company has seen "increased spontaneous reporting" of adverse effects in children this season in Australia. "We believe a lot of these reports were stimulated [by publicity about the problem]," she said, adding that there have been no reports of seizures in children ages 5 through 8.
ACIP Chair Carol Baker, MD, observed, "In the under 9 and over 5s, it appears you have more fever but no indication of more febrile convulsions, to summarize." The CSL representative agreed.
Concerning vaccine availability, Dr. Jeanne Santoli of the CDC commented that it's hard to predict availability for different age-groups, because there are a number of vaccines that can be used in multiple populations, and the CDC doesn't know who has ordered what.
Committee member Cody Meissner, MD, voiced concern about availability, given that flu vaccination is recommended for everyone from 6 months and older. "Will there be some kids in the 5 to 8 group for whom vaccine will not be available?" he asked.
"The answer is unknown," Baker replied. She added that there are spot shortages and kinks in the supply every year, but the overall national supply has never been a problem.
ACIP member Dr. Mark Sawyer and Uyeki said it is expected that Sanofi and MedImmune will be able to meet the need for vaccine for children 6 to 35 months old. Also, a Sanofi official at the meeting said the company has pediatric doses that are not yet allocated and may be able to fill the gap left by the removal of CSL's vaccine.
Santoli noted that the National Influenza Vaccine Summit has a Web site that tracks flu vaccine availability through reports from manufacturers and distributors. She said the site is www.preventinfluenza.org/ivats.
Dr. L.J. Tan of the American Medical Association, which hosts the site, said the site will be operating within a week or so.
The vote to pass the recommendation was 8-1, with two members abstaining. Uyeki said the formal recommendation will probably be published next week in Morbidity and Mortality Weekly Report.
Jul 30 CIDRAP News story "FDA approves flu vaccine as first doses ship"
Jun 1 CIDRAP News story "Australian flu-vaccine probe confirms increased reactions in small children"
ACIP members list