CDC Testing Three New Influenza B Vaccine Targets
Recombinomics Commentary 23:55
August 3, 2011

The CDC has released sequences at GISAID indicating it is testing three new seasonal influenza B vaccine targets, B/Hubei-Wujiagang/158/2009, B/Wisconsin/01/2010, B/Hong Kong/259/2010.  The first two are the Yokohama strain, while Hong Kong/59 is the Victoria strain.  This testing is somewhat unexpected because the vaccine selection committees for WHO as well as the FDA in the United States recommended leaving all three targets unchanged.  These committees have had problems in selecting the correct target for influenza B, and there was some discussion of producing a quadravalent vaccine, with two influenza B targets, one representing Yokohama and one Victoria strain. 

The testing of new targets for both strain increases this possibility, but the CDC is also testing a target for pandemic H3N2, raising the possibility of two vaccinations, one with three seasonal targets (H3N2 and two influenza B) and another for the two pandemic targets, H1N1 and H3N2 triple reassortants of swine origin..

The vaccine committee recommendations in February were controversial, because in the United States the death rate for Pneumonia and Influenza deaths was at record levels, which signal immunological escape from prior immunity in the population, which would include immunity due to vaccination.  When the P&I death rate rose to record levels in 2008, all three targets were changed, yet in 2011, all three were recommended to remain unchanged.

The 2011 recommendations were largely based on the antigenic characterization test, which can be heavily manipulated by the reference anti-sera or the isolation of emerging viruses. 

The sensitivity and specificity of the assays was also questionable after the fact, because the CDC is currently testing new candidates for all three current targets.  Unfortunately, the vaccine under production for the 2011/2012 season is nearing completion for shipment in the upcoming weeks.

Details of reasons for the testing of new targets for pandemic H1N1, seasonal H3N2, influenza B, and production of a pandemic trH3N2 vaccine would be useful.

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