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Paradigm Shift Intervention Monitoring
WHO Testing New Pandemic H1N1 Vaccine Target
The use of MDCK cells reduces the frequency of changes at key HA positions, such as 225 and 226 in the receptor binding domain, as well as positions 156-159 which are involved in immune recognition. The new CDC vaccine target also had K157E and two way testing using the old and new vaccine targets produced “LOW FAIL” results indicating the anti-sera against the old target, A/California/07/2009, had limited activity against the new target, and anti-sera against the new target had limited activity against the old target.
Last year an egg isolate of A/Victoria/502/2010 had D225G. The new vaccine target is wild type at position 225, but has Q226R.
The testing of new targets at this time is unusual because at the most recent meetings of the vaccine advisory committee for the US FDA, as well as the WHO meeting, recommended no changes in the three vaccine targets, and that vaccine for the 2011/2012 flu season in the northern hemisphere will be shipping shortly.
The testing of new targets by the CDC and WHO at this time raises serious concerns that the vaccine for the 2011/2012 season will have limited utility.