Influenza Vaccine Composition 2009-10 Northern Hemisphere Winter

The formulation of influenza vaccines is reviewed twice yearly by the World Health Organization (WHO).  The WHO recently recommended that composition of influenza virus vaccines for use in the 2009-2010 northern hemisphere influenza season should contain the following three virus strains(1):

• A(H1N1): an A/Brisbane/59/2007 (H1N1) - like strain
• A(H3N2): an A/Brisbane/10/2007 (H3N2) - like strain,
• B: a B/Brisbane/60/2008- like strain,

Note that:
This formulation differs from that for the 2009 Southern Hemisphere vaccine only with respect to the type B component.
The predominance of Brisbane strains in recent WHO recommended formulations is a reflection of the efficient collection of suitable virus samples for vaccine development and not of excessive influenza activity in that area.

Reference
(1) http://www.who.int/csr/disease/influenza/200902_recommendation.pdf