Pandemic H1N1 Virus Should Be Added to 2010-2011 Seasonal Influenza Vaccine, Says WHO

Robert Lowes

Authors and Disclosures 

February 18, 2010 — The World Health Organization (WHO) recommended today that the 2010-2011 seasonal influenza vaccines for the northern hemisphere should include a strain of the "dominant" pandemic A (H1N1) virus, as well as 2 nonpandemic influenza strains.
National public health authorities will decide whether to include a strain of the pandemic virus in the traditional trivalent vaccine or administer it separately as a monovalent vaccine, said Keiji Fukuda, MD, MPH, the special pandemic influenza advisor to the WHO director-general, at a press conference today.
WHO is dropping the older, nonpandemic seasonal A (H1N1) virus strain from its recommended mix because it does not expect this strain to circulate at significant levels.
The decision to replace the nonpandemic A (H1N1) strain with a pandemic strain was based on input from a WHO advisory committee composed of experts mostly from the laboratories and national public health agencies that make up the WHO Global Influenza Surveillance Network.
"In essence, what the scientists said was that in the past year, the overwhelming number of influenza viruses isolated around the world were the pandemic H1N1 virus," said Dr. Fukuda. "The experts believe, based on this information, that these viruses will continue to be one of the dominant viruses in the coming fall and winter season in the northern hemisphere."
Trivalent Vaccine with Pandemic Strain Makes Sense for Countries "That Use a Lot of Seasonal Flu Vaccine"
The 3 influenza strains recommended by WHO for northern hemisphere vaccines are an 

1) A/California/7/2009 (H1N1)–like virus, which is a pandemic strain; an 
2) A/Perth/16/2009 (H3N2)–like virus; and a 
3) B/Brisbane/60/2008-like virus.

In September 2009, WHO recommended these same strains for seasonal influenza vaccines for the southern hemisphere in 2010. WHO issues these recommendations for vaccine composition each September and February for the southern and northern hemispheres, respectively, for the coming influenza season.
If national public health authorities choose to use the pandemic strain for a monovalent vaccine, then the other 2 strains could make up a second vaccine.
Dr. Fukuda said a trivalent vaccine containing the pandemic virus would make sense for countries "that use a lot of seasonal flu vaccine."
Vaccine manufacturers and national governments, he said, would theoretically be able to use their current stockpiles of pandemic vaccines in bulk form for 2010-2011 seasonal vaccines in a trivalent formulation. In contrast, pandemic vaccine already packaged in vials and syringes could not be reused.
Dr. Fukuda emphasized that the recommendation to give seasonal-vaccine status to the pandemic influenza virus does not mean that the current pandemic is over. However, a WHO emergency committee will convene next week to decide whether the pandemic has entered an official "postpeak period," which means the worst is over, although the pandemic virus continues to cause sickness and even cause outbreaks in new regions. As proof, Dr. Fukuda noted that WHO has received new reports this week of communitywide transmission of the pandemic virus in Mauritania, which comes on the heels of outbreaks in neighboring Senegal.