Thursday, March 30, 2006

Doubt Cast on Stockpile of a Vaccine for Bird Flu

The New York Times
Doubt Cast on Stockpile of a Vaccine for Bird Flu

A bird flu vaccine being stockpiled by the government in preparation for a possible pandemic protects only about half the people who receive it, scientists are reporting. In addition, it must be given in such high doses that if a pandemic were to start soon, manufacturers could not begin to make enough vaccine for all who would need it.

A dose 12 times the amount used in a standard flu shot protected 54 percent of the people in a study being described today in The New England Journal of Medicine. That level of effectiveness is "poor to moderate at best," said Dr. Gregory A. Poland of the Mayo Clinic, who wrote an editorial accompanying the report.

But Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Disease, which paid for the development and testing of the vaccine, called the results "muted good news."

"We have a long way to go," Dr. Fauci said, but he said the research was a step in the right direction, adding, "You have to go through these early steps."

The new report is the first to include results on all the participants, 451 adults ages 18 to 64 who were inoculated at three medical centers in the United States. They received two shots a month apart. No serious side effects occurred, though some got sore arms from the shots.

Dr. Fauci and Dr. John Treanor of the University of Rochester, the lead investigator of the study, discussed the results on Tuesday in a telephone news conference.

The vaccine, developed by government and other researchers, is being made by Sanofi Pasteur under a government contract. It is designed to prevent the disease caused by the A(H5N1) virus, which has been spreading rapidly through Asia, Europe and Africa. The disease has not reached the Americas.

The virus attacks mainly birds, but some humans have been infected, almost all of them through contact with birds, and half have died. Some health officials are concerned that the virus could mutate in a way that would make it more contagious in people and start a lethal pandemic.

Vaccines work by activating a patient's immune system. Standard flu shots, even with their smaller doses, are more effective than the new bird-flu vaccine: they protect 75 percent to 90 percent of people under 65, and 50 percent to 60 percent of those who are older, Dr. Fauci said.

The standard shots probably work better because the viruses they protect against have been around for a long time, and most adults have some immunity to them. The vaccine acts like a booster shot to enhance an immunity that is already there.

Researchers say the bird flu vaccine may be less effective because hardly anyone in the United States has been exposed to the A(H5N1) virus. People have no resistance to it, and so it takes a lot of vaccine to jump-start the immune system.

The study used blood tests, which measured immunity to the virus, and researchers set the bar fairly high. Dr. Treanor said he thought that the vaccine might actually work better than it appeared from the study.

A next step in the research is to try adding a substance called an adjuvant to the vaccine, to try to make it work better and at lower doses. Adjuvants stir up the immune system. Alum is a common one.

The government has stored a "modest" amount of the Sanofi vaccine, Dr. Fauci said, about seven million to eight million doses. He said that such a small amount would not be of much help to the public, but he described it as stopgap.

If the disease emerged, he said, the main purpose of the supply would be to inoculate health care workers and people involved in the rush to make a vaccine specific for the virus strain causing the outbreak.

Currently, the United States does not have the production capacity to make bird flu vaccine and the usual vaccines for seasonal flu.

The bird flu vaccine can be made only between runs of the seasonal vaccines, which have to take priority because those types of flu occur every year, and bird flu is a theoretical threat.

Dr. Fauci said the government was spending several hundred million dollars to increase the nation's ability to make flu vaccine.

Another company, Chiron, also has a government contract to make millions of doses of bird flu vaccine. But Chiron, which has a history of manufacturing problems, has produced only 70 percent of the amount it promised the government it would provide by now, and it will not begin making the rest until this fall.