Bird-flu vaccine 'may not work on humans'

The bird-flu vaccine currently being manufactured was effective against at least two forms of the virus in experiments with mice, but it is not clear if it would also work for humans, a US health chief says.

US government experiments have shown that the clade 1 vaccine also prevented proliferation of the clade 2 virus, a version seen more recently in Indonesia, Europe and Africa, in mice, said Dr Nancy Cox, of the Centres for Disease Control and Prevention.

But that did not mean humans would necessarily get the same result, she said.

“You can’t necessarily extrapolate from animals to humans. It’s relatively easy to protect mice,” said Cox, director of the CDC’s influenza branch.

In another test with ferrets, which did not involve giving an animal vaccine, CDC researchers found that the immune defences developed by a ferret against the clade 1 bird flu were not effective against the clade 2 bug.

The animal test results were discussed yesterday at an international conference in Atlanta, Georgia, on emerging infectious diseases.

Worldwide, 177 human cases of bird flu have been reported, including 98 deaths, according to researchers at the conference. The different forms of bird flu seem to have descended from a virus found in Chinese geese in 1996, CDC officials said.

That influenza did not make people ill. But since then, four groups, or clades, of the virus have been identified that have caused human illness and death. Nearly all those cases are clade 1 and clade 2.

The US government is spending £140m (€201.5m) for about eight million doses against the Vietnamese version of bird flu, but has plans for enough vaccine to protect 20 million Americans.