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U.S. Approves 1st Bird Flu Vaccine

Called an 'interim' measure, it was effective about half the time in trials

TUESDAY, April 17, 2007 (HealthDay News) -- U.S. health officials announced on Tuesday that they have approved the first vaccine for humans against bird flu.

The vaccine, which in clinical trials proved to be effective about half of the time, will not be available commercially but several million doses are being purchased by the federal government for inclusion in the U.S. Strategic National Stockpile, maintained by the U.S. Centers for Disease Control and Prevention.

"The threat of influenza pandemic is one of the most important public health issues our nation faces today," Norman Baylor, director of the U.S. Food and Drug Administration's Office of Vaccines Research and Review, said at a teleconference. "This approval is an important step in enhancing the nation's readiness against a possible pandemic and enhances our ability to protect those who could be at increased risk of exposure."

In the past two years, the H5N1 strain of avian flu has infected poultry throughout Southeast Asia, Central Asia, Africa and Europe, prompting the destruction of millions of birds. So far, more than 100 people have died worldwide from H5N1 infection, which has been spread through close contact with birds.

The big worry among health officials is that the virus will acquire the ability to jump easily between humans, leading to a pandemic and millions of deaths. Unlike the seasonal flu, humans have no immunity to bird flu.

To prepare for such a scenario, the U.S. government has already contracted with drug maker Sanofi Pasteur to produce $100 million worth of the newly approved avian flu vaccine.

A trial of the vaccine, published in the March 30 issue of the New England Journal of Medicine, reported that only about half of the people receiving the shot produced antibodies indicating that they were protected. Even this modest effect required extremely high doses -- about 12 times that of the annual flu vaccine.

Officials acknowledged that the results were not all they had hoped for.

"Ideally, yes, you would like to have a vaccine with higher efficacy," Baylor said. "The vaccine is safe and effective, but it's two doses over 28 days and you'd like to be able to respond to a pandemic quicker than that, and ideally would like to have a vaccine that you could have one dose and need less antigen. Research is ongoing in that area to improve the vaccine but, at this point, this is where we are."

The new vaccine is indicated for people aged 18 to 64 who are at "increased risk" of exposure to the H5N1 virus. Individuals would get two injections of 90 micrograms each, spaced about one month apart.

According to Baylor, "increased risk" is defined by governmental policy makers and might probably include military personnel and others who might be entering areas where the virus is present.

"Having a vaccine that would require 90 micrograms twice, in and of itself, would not and could not be the answer to where we want to be," Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID), said when the New England Journal article was published. "It is a step forward, but it is a small step," he said.

An accompanying editorial in the journal called the response "poor to moderate at best."

The study was funded by NIAID.

Because the vaccine is now licensed, it does not require informed consent when it is used, Baylor said.

"There are several newer vaccines under development," he said. "This is sort of an interim measure. This will allow us to have a vaccine."

More information

The U.S. Centers for Disease Control and Prevention can tell you more about avian flu.

SOURCES: April 17, 2007, teleconference with Norman Baylor, Ph.D., director, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, Md.
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