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|Paradigm Shift Intervention Monitoring||Audio: Apr21 Sep22
Clade 7 Vaccine Failures Raise China Concerns
The above comments describe the Jiangsu December outbreaks which involved H5N1 closely related to clade 7 isolates from a 2006 outbreak in Shanxi. As noted above, the outbreak in Jiangsu led to additional vaccination of flocks in adjacent provinces.
However, shortly after the Jiangsu outbreak, human cases were reported throughout China (see updated map), and comments from the news conference in Hong Kong strongly suggested that the human cases were a “northern strain” which would almost certainly be clade 7, which has been reported in multiple northern provinces. The news conference also strong suggested the human cases were not caused by 2 Fujian sub-clades, 2.3.2 and 2.3.4, which had previously been linked to the vast majority of prior human cases in China.
Previously, the only reported human clade 7 case was in Beijing in 2003, so 9-12 cases in China and Beijing in the brief period following the Jiangsu outbreak would represent a dramatic rise in clade 7 cases, and the location of the cases would suggest that clade 7 has spread throughout China and not limited to the re-vaccinated provinces adjacent to Jiangsu.
Reports of clade 7 in northern Vietnam also support the spread of clade 7 this season, further supporting widespread clade 7 in poultry.
However, as noted above, the clade 7 was detected during routine surveillance and the OIE report indicated the poultry was asymptomatic, raising detection / reporting issues. Indeed there have been no reports from China on additional H5N1 outbreaks and sequences from the Jiangsu poultry outbreaks or the confirmed human cases have not been released. Comments on A/Beijing/1/2009 only stated that there had been no reassortment with human flu genes and the variations in the sequence were minor.
Prior clade 7 sequences from Shanxi and Hunan had a large number of receptor binding domain changes, and minor changes in these sequences can have major effects of virulence and transmissibility. Therefore, release of the sequences from China, as well as sequences from human and poultry cases would be useful. Similarly, WHO has withheld the sequence of its clade 7 vaccine target, which was from a 2008 poultry isolate in Vietnam.
The lack of transparency on clade 7 sequences remains a concern. And the withholding of the sequence of the WHO vaccine target sets a poor example of transparency, which is of significant concern due to the number of clade 7 cases and clusters coupled with the vaccine failures noted above.