The conclusion that the D225G in the April samples, including A/California/7/2009, may have influenced the decision to select X-181A, which lacks D225G, as the killed vaccine. target. This absence is likely linked to the low yields that led to vaccine shipment delays resulting in the delivery of most vaccine after the fall peak in cases. In contrast, the live attenuated vaccine made by MedImmune had D225G and grew well in eggs, leading to shipment weeks ahead of the killed vaccine.
Thus, the CDC conclusion that D225G identified in eggs was a lab artifact may have had significant consequences regarding the selection of the vaccine target in April, as well as the recent recommendation that the vaccine can be used in the 2010/2011 season, when D225G may be much more prevalent and killing many more people.
via CDC On D225G In Egg Isolates Raises H1N1 Vaccine Concerns.