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Flu Vaccine Efficacy Against H3N2 Wellington Threaten Supplies

Recombinomics Commentary
March 11, 2005

>> Principal medical adviser for Medsafe Dr Stewart Jessamine said the information was "unexpected and disappointing". He said it was too early to comment on whether lives could be put at risk because of the delay.

Yesterday the National Party warned the delay had created potentially the most serious public health crisis in New Zealand for many years.

Health spokesman Dr Paul Hutchison said it could be difficult to find an alternative vaccine source and lives could be put at risk.

Dr Hutchison said GPs were compiling lists of vulnerable elderly, asthmatics and hospital workers but were unable to tell them when they could get the vaccine.

A spokesman for Sanofi-Pasteur said the company would be in a better position to comment after Monday's meeting.

Dr Jessamine said that although the vaccine would protect against two of the three strains most likely to be in circulation in New Zealand it may not protect people against the third strain, known as A/Wellington/2004(H3N2). <<

The rapid evolution of H3N2 is forcing vaccine manufacturers to stay nimble to try to keep pace, and this seems to be causing significant problems. For five years A/Panama/2007/99 represented the H3N2 component of the human trivalent vaccine.  When the Fujian strain began to emerge in 2002, a recommendation was made to switch from Panama to Fujian.  However, because of problems growing Fujian, Panama was used last year.  Fujian became the dominant strain, and the effectiveness of the Panama vaccine was less than ideal.  In the southern hemisphere, a new strain, Wellington, began to replace Fujian, so the vaccine for the southern hemisphere was switched to Wellington and now there are questions about the effectiveness of the new vaccine.

In the northern hemisphere, the California strain began to replace Fujian. In the United States California created a second wave of infections this season.  For the past 4 reporting periods, California has dominated in the antigen characterization tests in the US.  Detection has been 17-0, 54-0, 38-7, and 21-3 for California over Fujian (Wyoming is the Fujian like strain in the US).   The emergence of California in the United States correlated with clusters of student deaths, primarily from bacterial meningitis complications in flu patients.

Similar antigenic characterization tests have shown that the California strain has spread worldwide.  However, California was isolated in Sept 2004, and more recent isolates have evolved even further from Fujian.  California has been selected for next season's Northern hemisphere's H3N2 strain, but the rapid evolution, coupled with the problems being reported on the effectiveness of the new vaccine against Wellington raise serious questions about next season.

Although the California strain was isolated in Santa Clara California, it appears to have begun to emerge in 2003 in Zhegiang Province in China as well as Taiwan.  More evolved versions have been detected in 2004 in Bangkok, Thailand, raising the possibility of dual infections involving virulent California H3N2 and the fatal bird flu strain H5N1.

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