Testing Three New Influenza B Vaccine Targets
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
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
H3N2, influenza B, and production of a pandemic trH3N2 vaccine
would be useful.
at Nature Precedings