Flu B Virus Strain Victoria Is Good Choice As Vaccine Component - Wyeth

Wyeth's preliminary data on B/Victoria/504/2000 suggest that it is "an excellent strain" for use in the manufacture of the trivalent flu vaccine.

"Looking at early passage data we agree that B/Victoria is an excellent strain," Wyeth-Lederle Associate Director-Process Improvement Richard Hjorth, PhD, said at a meeting of FDA's Vaccines & Related Biological Products Advisory Committee Jan. 30 to decide the formulation for the 2001-2002 influenza vaccine.

The committee recommended that the influenza B vaccine strain used in the manufacture of flu vaccine for 2000, B/Yamanashi/98, be replaced, but deferred on whether the substitute should be B/Victoria/504/2000.

Centers for Disease Control & Prevention Influenza Branch Chief Nancy Cox, PhD, noted that there is an antigenic drift from B/Yamanashi/98.

Although most committee members agreed that B/Victoria/504/2000 would be an acceptable choice, they requested additional data on new Chinese strains. Analyses of new Chinese influenza B viruses would be available within the next two to three weeks, Cox said.

The Victoria strain was used to manufacture vaccines during the flu season in the Southern Hemisphere, along with B/Johannesburg/5/99. "Unfortunately B/Johannesburg/5/99 gives a low yield [while] B/Victoria/504/2000 gives a moderate yield," Center for Biologics Evaluation & Research Medical Officer Zhiping Ye, MD/PhD, said.

The committee was unanimous in recommending that the incumbent influenza A vaccine strain be retained for both the H1N1 component (A/New Caledonia/99) and the H3N2 component (A/Panama/99) because no clear alternate could be identified. The recommendation could be changed if a better variant strain is identified in the next two to three weeks.

Both A/New Caledonia/99 and A/Panama/99 strains are "immunogenic and well matched to currently circulating viruses," Cox said. The manufacturing processes for the two strains are also well defined and predictable, she added.

Although Aventis agreed with Wyeth's assessment of B/Victoria, "we are...extrapolating the ability to produce vaccine from very limited data, just hemagglutination data," Aventis Pasteur representative Greg Slusaw said. "There is some historical precedent that it is a somewhat valid way of anticipating how well they will remain but it is almost an order of magnitude guess."

The committee also deliberated on whether a decision to defer recommendation of a strain for the influenza B component of the vaccine would affect production.

Whether a change in strain would adversely affect production "would depend on how far we got with a strain before you change it," Hjorth said.

"If we were just doing isolate development then that would be great. If we are actually manufacturing then those eggs are gone forever. If the new strain would have a better yield then we would be happy to throw out two weeks of vaccine."

Slusaw noted that changes in vaccine composition had an additive effect in delaying production. "Even though we typically change one or more components [each year] that doesn't change the fact that we are taking a bit of a gamble every time we do it."

"A change several months into the season [would] be catastrophic, especially if we are starting with a new seed virus, something that we haven't prepared for," Slusaw said. "At least having things to work with earlier helps identify potential."

If there were no changes in the vaccine strain, then "from a manufacturing standpoint, it probably is a slam dunk," Slusaw said.

Slusaw was listed in the agenda as representing the Pharmaceutical Research & Manufacturers of America but noted that he was "representing Aventis Pasteur, not necessarily the views of PhRMA, simply because all PhRMA flu manufacturing members did not have a chance to review what I'm saying today."

"One of the reasons why we did not fully get together on this is that some of the data just came out yesterday," Hjorth said.

Manufacturer compliance problems and lower than expected yields of flu vaccine strains delayed the supply of the flu vaccine last year.