Avian Flu Vaccine Called Effective in Human Testing August 7, 2005By LAWRENCE K. ALTMAN
New York Times
WASHINGTON - Government scientists say they have successfully tested in people a vaccine that they believe can protect against the strain of avian influenza that is spreading in birds through Asia and Russia.
Health officials have been racing to develop a vaccine because they worry that if that strain mutated and combined with a human influenza virus to create a new virus, it could spread rapidly through the world. (The vaccine cannot lead to such a situation because it is made from killed virus.)
Tens of millions of birds have died from infection with the virus and culling to prevent the spread of the virus. About 100 people have been infected, and about 50 have died from this strain of the avian influenza virus, called A(H5N1). So far there has been no sustained human-to-human transmission, but that is what health officials fear, because it could cause a pandemic. And that fear has driven the intense research to develop a vaccine.
The director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony S. Fauci, said that although the vaccine that had undergone preliminary tests could be used on an emergency basis if a pandemic developed, it would still be several months before that vaccine was tested further and, if licensed, offered to the public.
"It's good news," Dr. Fauci said. "We have a vaccine."
But he cautioned: "We don't have all the vaccine we need to meet the possible demand. The critical issue now is, can we make enough vaccine, given the well-known inability of the vaccine industry to make enough vaccine?"
An earlier human vaccine against the A(H5N1) avian influenza virus was prepared after it first appeared in the world, in Hong Kong in 1997. That vaccine was never fully developed or used, and the strain has mutated since then.
In interviews over recent days, Dr. Fauci has said that tests so far had shown that the new vaccine produced a strong immune response among the small group of healthy adults under age 65 who volunteered to receive it, although the doses needed were higher than in the standard influenza vaccine offered each year. The vaccine, developed with genetic engineering techniques, is intended to protect against infection, not to treat those who are sick.
Further tests are expected to be conducted among two groups - people 65 and older, and children - over the next several months. Dr. Fauci expressed confidence that they would confirm the success of the first tests and answer remaining scientific questions.
Because the vaccine is made in chicken eggs, "a potential major stumbling block" to successful mass production is the number of eggs farmers can supply manufacturers, Dr. Fauci said.
If manufacturers can overcome such hurdles, the new vaccine could go far in averting a possible pandemic of human influenza, Dr. Fauci said.
Only a small number of human cases of A(H5N1) influenza have been found. Although a few cases may have been transmitted from person to person in Asia, the A(H5N1) strain has not garnered enough strength to spread widely among humans anywhere.
As of Friday night, according to the World Health Organization in Geneva, the avian strain has killed 57 of the 112 people it has been known to infect in four countries. They are Cambodia (4 cases), Indonesia (one case), Thailand (17 cases) and Vietnam (90 cases).
The additional tests are needed in part to determine the optimal dose of vaccine; how many shots people will need for protection; and whether adding another ingredient called an adjuvant to the vaccine could raise the potency of lower doses, stretching the number of people that could be protected. Even when these tests are completed, more time will be needed before the Food and Drug Administration can license the human vaccine and before policy makers determine when and how it should be administered.
Government researchers and others developed the vaccine, which is produced by Sanofi-Pasteur, a French vaccine company that is now part of Aventis. The government could decide to release the product under emergency conditions if an A(H5N1) influenza pandemic struck before the testing process was completed.
Although cautioning that the vaccine had not been fully tested, Dr. Fauci said that the initial test findings had given the federal government enough confidence to start the process of adding millions more doses of the vaccine to the 2 million it had bought. The present supply is stored in bulk form, and "we cannot put it in vials until we find out what the right dose is," Dr. Fauci said.
The manufacturer needs to know the dose and regimen to determine how much more vaccine it can produce and make available to the United States and other customers.
Scientists had to test the human avian influenza vaccine on volunteers because the A(H5N1) strain differed in significant ways from the conventional strains that cause human influenza.
Also, the influenza shots that are offered each year are derived from the human strains that are circulating most widely at the time experts choose the components of the next vaccine. Human influenza viruses mutate enough each year to force changes in the standard vaccines. Such vaccines produce a broader and stronger immunity because recipients build up an immunity to influenza from repeated immunizations and exposure to the influenza virus.
In a sense, the standard annual influenza shots are booster doses. But the A(H5N1) vaccine is a primary immunization because, having had no exposure to that virus, people lack any immunity to the avian strain.
The United States is thought to be the only country that has produced a human vaccine against the A(H5N1) influenza strain. Australia, Canada, France and Japan are among countries where scientists are trying to develop human avian influenza vaccines, according to the World Health Organization.
Dr. Fauci's institute also contracted with the Chiron Corporation, which is based in Emeryville, Calif. to make another A(H5N1) vaccine. But tests of the Chiron vaccine have not started because of delays related to prior contamination found in Chiron's plants.
Dr. Fauci said his institute had 8,000 doses of the Chiron human A(H5N1) vaccine and hoped to start testing it in volunteers in late fall. The tests will follow the same steps taken with the Sanofi-Pasteur vaccine, he said.
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