Bird flu mutation impacting vaccine planning

As always, CIDRAP News is on top of all things avian flu-related. This story from Friday covers the WHO announcement of the most recent data on avian flu mutation and the specific strains that are recommended targets of future vaccine development. Here's the WHO document.

The CIDRAP story offers a nice analysis of the relevant policy and planning ramifications of the science-laden WHO document. Here's an excerpt, featuring comments from Dr. Michael Osterholm:

"Many experts who follow the ongoing analysis of the H5N1 virus sequences are alarmed at how fast the virus is evolving into an increasingly more complex network of clades and subclades, Osterholm said. The evolving nature of the virus complicates vaccine planning. He said if an avian influenza pandemic emerges, a strain-specific vaccine will need to be developed to treat the disease."

That the virus will continue to evolve has long been known, as has the fact that vaccines developed in advance of a pandemic are likely to be increasingly less effective as time passes. For those hoping that a vaccine currently in development would be the vaccine, this news confirms that such hopes are unrealistic. The vaccines in the pipeline today are based on clade 1 strains of the virus, while most recent human cases have been caused by clade 2 strains, according to the WHO report. While it remains unclear how effective "older" vaccines will be against the eventual pandemic strain (if one develops at all), nearly all continue to agree that the most effective vaccine can only be developed after a human pandemic begins.

The WHO document cited here provides our most specific knowledge to date of the virus' pattern of mutation, information needed to develop effective vaccines. It also makes mention of the potential to develop region-specific vaccines if the virus' mutation proceeds in such a way in the months and years ahead.