BETHESDA, Md. The Food and Drug Administration's (FDA) Committee for Biologics Evaluation and Research Vaccines and Related Biological Products Advisory Committee recently agreed on the two remaining components of next year's trivalent influenza vaccine.
After reviewing recent surveillance and laboratory data, the committee unanimously agreed on the two influenza A components in a recent meeting at CBER. For the H3N2 component, the committee recommended retaining last year's A/Nanchang/933/95 strain to represent the A/Wuhan/358/95-like strain.
"I see no compelling reason to change this strain," said Dixie E. Snider Jr., MD, CDC associate director of science.
However, concerning the A/Bayern/7/95-like strain (1N1), the committee recommended the Centers for Disease Control and Prevention (CDC) and FDA researchers continue working to identify a strain with suitable antigenic and growth characteristics.
"The recommendation supports making an effort to identify a strain to update the H1N1 strain, but we're not sure yet which strain will be the best," explained Theodore Eickhoff, MD, temporary committee member, professor of medicine, University of Colorado Health Sciences Center.
If a high-yielding strain is not found, the committee unanimously agreed to recommend using last year's A/Texas/36/91 strain, according to Eickhoff.
Roland A. Levandowski, MD, supervisory medical officer, CBER, said there are at least four possible high-yielding reassortants for the H1N1 strain, but that doesn't guarantee any of them will be suitable for manufacturing.
"This information changes daily," he said. "We are at the stage of scrambling to try and get this information together and everybody is working quite hard to fill in the blanks that still exist for the strains."
An appropriate high-yielding strain needs to be found within approximately four weeks, Eickhoff said, for manufacturing to proceed on schedule.
The committee originally postponed the recommendation because of the lack of influenza A(H1N1) strains present in the United States during this year's influenza season. According to World Health Organization (WHO) collaborating laboratories, 93.4% of influenza isolates tested were type A and 6.7% were type B. All influenza type A isolates subtyped were A(H3N2) and no type A(H1N1) were reported in the United States during the 1996-97 influenza season.
"We haven't had many new H1N1 viruses to examine," explained Nancy Cox, PhD, chief of the influenza branch, CDC. "There have been so few viruses isolated worldwide."
The committee recommended in January that the vaccine's B component remain the same as last year's strain: B/Harbin/7/94.
"Subsequent testing has been very reassuring. The bottom line is that nothing has changed since our January meeting, and our selection of the Harbin strain looks very solid," Cox said.
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