Live AI vaccine has potential
When tested in mice and ferrets, experimental
vaccines based on live, weakened versions of different strains of the H5N1 avian
influenza virus were well-tolerated and protected the animals from a deadly
infection with naturally occurring H5N1 flu viruses.
These findings, which appear in the September 12 issue of PLoS Medicine,
are also encouraging, the researchers say, because they demonstrate the ability
to create a vaccine based on one particular strain of the H5N1 bird
virus that could potentially protect against different emerging H5N1 flu
"If an influenza pandemic were imminent or under way, we would need a
vaccine that could stimulate immunity quickly, preferably with a single dose,"
says NIAID Director Anthony Fauci. "Vaccines based on live but weakened versions
of the H5N1 avian influenza virus may quickly stimulate protective
The NIAID and MedImmune research team created three vaccines by combining
modified proteins derived from virulent H5N1 flu viruses with proteins from an
artificially weakened (attenuated) flu strain. The virulent H5N1 viruses were
isolated from human cases in Hong Kong in 1997 and 2003, and Vietnam in 2004.
The attenuated flu vaccine strain was lab-grown in progressively colder
temperatures ("cold-adapted") to prevent the resulting vaccine viruses from
spreading beyond the relatively cool upper respiratory
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