H3N2 California 7 Infecting Vaccinated Nurses in Canada?
Recombinomics Commentary
February 26, 2005
>> But there are some reports of vaccinated nursing staff in Ontario coming down with a flu-like illness at rates higher than should be expected. and that suggests protection against the new strain may, in fact, be minimal.
Dr. Donald Low admits it's unknown how much protection this year's flu shot offers.
"We don't know yet just how much protection that the vaccine we provided this year is going to provide protection against this new strain."
Unfortunately, it could take until the end of flu season, likely sometime in May, before scientists will be able to provide a better answer. <<
The better answer was provided today in WHO's WER. It includes a table showing how antisera against various isolates cross-react with the three H3N2 serotypes in current or future vaccines. A/Wyoming/3/2003 represents the original Fujian strain from 2002 and it is in the current vaccine. A/Wellington/1/2004 has evolved away from Fujian, and is in the vaccine being prepared for the Southern Hemisphere. A/California/7/2004 has evolved even more. It is being used in the Northern Hemisphere vaccine for next season.
The data released today shows that California-like H3N2 is being detected worldwide. Ratios of titers against California/Fujian or California/Wellington are getting larger, showing more evolution. The two isolates with the largest ratios are from Wisconsin in 2004 and Iceland in 2005. The higher the ratio, the less protection from the current vaccine. This may be accounting for immunized health care workers getting sick in Canada, as well as clusters of student and soldier deaths in Eastern Pennsylvania and North Carolina. The California strain has accounted for all of the isolates subjected to antigenic analysis in the US for the last two reporting periods. This has been associated with a number of deaths in children and young adults throughout the US.
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