FDA selects pandemic H1N1 for 2010-11 seasonal flu vaccine

Feb 22, 2010 (CIDRAP News) – The US Food and Drug Administration's (FDA's) vaccines committee voted today to follow the World Health Organization's advice and fold the pandemic H1N1 influenza vaccine into the seasonal flu vaccine for next season.

The FDA Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously to recommend that the pandemic virus become the influenza A/H1N1 component of the 2010-11 vaccine, according to FDA spokeswoman Shelly Burgess. Barring major surprises, that means there will be just one flu vaccine next fall instead of the two vaccines—pandemic and seasonal—that were made for the current flu season.

The committee also went along with the WHO's recommendation last week to switch the A/H3N2 component of the trivalent (three-strain) vaccine from the Brisbane strain to a 2009 Perth strain, Burgess reported.

In addition, the VRBPAC voted to keep the influenza B strain used in the 2009-10 vaccine, a 2008 Brisbane strain, as the WHO had advised, she said.

The WHO and FDA normally pick flu strains for the Northern Hemisphere in February because it takes months to develop vaccine viruses based on the circulating strains, grow large quantities of them in chicken eggs, and formulate them into vaccines. Most flu vaccines are still produced by the decades-old egg-based method.

The committee recommendation comes as pandemic H1N1 cases continue to decline and seasonal flu strains are scarce in much of the Northern Hemisphere, though some type B activity has been reported in China. Pandemic flu strains typically continue to be predominant in the first few years after their emergence, experts say.

The strains chosen by the FDA panel today, according to Burgess, are:

  • For the H1N1 component, an A/California7/2009-like virus (the pandemic strain), which replaces A/Brisbane/59/2007
  • For H3N2, an A/Perth/16/2009-like virus (an example is A/Wisconsin/15/2009), which replaces A/Brisbane/10/2007
  • For type B, a Brisbane/60/2008-like strain (the same as last year)

These are the same three strains the WHO picked last September for the 2010 Southern Hemisphere flu season, which typically begins in May.

CLS Ltd., an Australian vaccine company, is currently producing trivalent vaccine for the Southern Hemisphere's season. Bill Cracknell, who is director of the company's influenza operations and attended the VRBPAC meeting, said today that CSL hasn't had any major production glitches but that yields of the three flu strains have not been great.

"It's been less than spectacular," he told CIDRAP News, but added that he doesn't expect problems making the vaccine for the Northern Hemisphere season.

Cracknell said CSL is using a Wisconsin strain, part of the Perth family, for the H3N2 component, but will switch to another related strain for Northern Hemisphere production in the hope of getting better yields.

He said the VRBPAC meeting brought no surprises. "I guess the whole meeting proceeded really as you would've expected it to, coming out of a season in which one strain knocked everything else's socks off," he commented.

Dr. Nancy Cox, director of the Centers for Disease Control and Prevention's Influenza Division, told the committee that the previous H1N1 strain "most likely poses a low risk in the forthcoming Northern Hemisphere season," according to a Bloomberg News report published today.

The WHO announced its flu vaccine recommendation Feb 18, after a 4-day meeting of experts from the agency's collaborating laboratories and national regulatory authorities. The VRBPAC routinely follows the WHO advice on the strains to put in the vaccine.

See also:

Feb 18 CIDRAP News story "WHO picks pandemic strain for next seasonal flu vaccine"

Sep 23, 2009, CIDRAP News story "WHO picks novel H1N1 for 2010 southern hemisphere flu vaccine"

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