Five viruses (0.3%) tested showed reduced titers with antiserum produced against A/California/07/2009.
The above comment from today’s CDC week 8 report indicates the number of low reactors reported by the CDC has jumped from 2 to 5 in a week that reflected an all time low in H1N1 testing. The per cent positive is on the rise and is at the highest level in 2010, and as high as it has been since mid-December (week 50), so the number of positive samples is up, in spite of the very limited testing.
Increases in low reactors are expected as the H1N1 evolves away from the current immunity as well as the California/7 based vaccine.
via Jump In H1N1 Low Reactors In United States Raises Concerns.