Flu vaccine researchers find 1 dose works

U.S. and Australian researchers said late Thursday that the flu vaccine they have been testing for months not only works but is effective with adults after just one dose, raising the prospect that even a limited supply of the vaccine could go further than expected.

Scientists have been warning for months that the H1N1 flu, also known as the swine flu, could reach epidemic proportions during this year’s flu season and that multiple shots of vaccine might be required to combat its spread.

But they now think that a single dose will be enough to protect an adult within 10 days of its application, a fact that will mean that millions more Americans will likely be protected this fall than authorities had expected just weeks ago.

“There was a concern that people would require two doses of the vaccine or that we would not even have a vaccine that induces a response,” said Dr. Anthony Fauci of the National Institutes of Health. “Not only does it induce a response, but it does it very potently.”

Australian vaccine manufacturer CSL Ltd. on Thursday published results of a study in the New England Journal of Medicine that found between 75 percent and 96 percent of vaccinated people should be protected with a single dose, half the amount of vaccine that scientists recently thought would be effective.

On Friday, U.S. data are scheduled to be released that show a similar result. In fact, protection after a single shot could start as soon as eight days after it is applied, Dr. Fauci said of the U.S. findings.

He said researchers would know more about dosing for children within two weeks.

The findings from both countries are important because authorities recently announced that only limited supplies of the vaccine would be available early this fall. Only a third of the amount of vaccine that authorities had hoped to have by mid-October was actually planned to be shipped.

The studies offer hope that many more Americans can be vaccinated despite the scarce supply.

“This is good news for supply for ourselves and globally,” said Dr. Fauci, director of the National Institute of Allergy and Infectious Diseases who is spearheading U.S. testing of the vaccine.

The Department of Health and Human Services has awarded nearly $2 billion in contracts this year to five pharmaceutical companies, including CSL, for bulk production of the vaccine and related materials.

But the companies have not been able to boost supplies quickly because of the rate at which the vaccine grows in its host chicken eggs.

“It’s growing slowly. We originally thought we would have 160 million doses by mid-October,” he said. “It’s just going to take a little longer to get there.”

The U.S. Centers for Disease Control and Prevention in Atlanta says swine flu is the world’s fastest-moving influenza pandemic, moving through 177 countries since it was identified four months ago.

New York City health authorities estimate that more than 1 million residents have already been infected.

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