H1N1 in Transition: WHO to Decide Post-Peak Phase in H1N1 Pandemic; 2009 H1N1 Replaces Seasonal A H1N1 in Next Trivalent Influenza Vaccine

This week, the World Health Organization (WHO) Emergency Committee will advise on transition to a “post-peak” phase for the H1N1 pandemic. The current pandemic alert level is at Level 6.

The committee ruled out a “post-pandemic” phase because, in its view, H1N1 is not yet behaving like normal seasonal infuenza, and that future waves of H1N1 were possible. WHO’s decision will be made public at 1000 GMT on 24 Feb.

Meanwhile, H1N1 has peaked and is waning across the globe. Pockets of “active, but declining H1N1 transmission persist in southern/eastern Europe as well South/East Asia.” Influenza B virus is circulating at elevated levels in China, displacing H1N1. H3N2 is co-circulating at low levels in Asia and China. H1N1 is the predominant strain in the Americas; flu activity in the USA is below baseline.

Last week WHO also recommended that A(H1N1) 2009 replace seasonal (A)H1N1 in the 2010-2011 trivalent seasonal influenza vaccine. As summarized by CIDRAP, the specific WHO recommendations were:

  • H1N1 component: a strain similar to A/California/7/2009, replacing A/Brisbane/59/2007
  • H3N2 component: a strain similar A/Perth/16/2009, replacing A/Brisbane/10/2007*
  • B component: a strain similar to B/Brisbane/60/2008-like virus

* A/Wisconsin/15/2009 is a A/Perth/16/2009 (H3N2)-like virus and is a 2010 southern hemisphere vaccine virus.

Oseltamivir (Tamiflu) resistance in pandemic A(H1N1) 2009 viruses has been limited. However, WHO also noted “the majority of seasonal A(H1N1) viruses were oseltamivir resistant.” This resistance developed during the 2008-2009 flu season.

COMMENT: Flu watchers understandably keep an anxious eye on hot-zone countries like Indonesia, Vietnam and Egypt where H5N1 (avian flu) and H1N1 are in co-circulation, carrying potential for a pathogenic virus reassortment. The WHO report serves as a reminder that a reassortment between 2009 H1N1 and antiviral-resistant seasonal H1N1 viruses would also be an unwelcome development.

Life Extension - Health And Medical Findings

CIDRAP: CDC flu barometers show level activity
CIDRAP: WHO picks pandemic strain for next seasonal flu vaccine
Reuters: WHO may declare post-peak pandemic phase next week
Reuters: WHO to decide new flu vaccine formula
WHO: Pandemic (H1N1) 2009 – update 88
WHO: Recommended viruses for influenza vaccines for use in the 2010-2011 northern hemisphere influenza season (PDF)

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  1. […] By WHO protocol, any public announcement is embargoed until after the Director-General informs the 193 member states of the decision. Formal announcement is expected on 24 Feb at 1000 GMT. […]

  2. […] the Norwegian data suggests an upper-bound on the incidence of this mutation in severe disease. Seasonal H1N1 influenza viruses are now completely resistant to oseltamivir and this is a likely evolutionary path for future pH1N1 […]