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Consumer Update |
On April 17, 2007, FDA announced the first approval in the United States of a vaccine for humans against the H5N1 influenza virus, commonly known as avian influenza or "bird flu."
The vaccine could be used if the current H5N1 avian virus were to mutate into a form that could spread easily from human to human, triggering a pandemic. An influenza pandemic is a worldwide outbreak of disease that occurs when a new strain of influenza virus circulates and causes serious illness in large numbers of people.
"The timing and severity of an influenza pandemic is uncertain, but the danger remains very real," says Jesse Goodman, M.D., M.P.H., Director of FDA's Center for Biologics Evaluation and Research.
If a pandemic occurs, the approved vaccine may provide early, limited protection in the months before a vaccine tailored to the pandemic influenza virus subtype (strain) could be developed and produced.
If a pandemic strain is substantially different from the H5N1 virus contained in the vaccine—or if the pandemic is caused by a strain that does not belong to the H5N1 subtype—the newly approved vaccine would probably not be effective and scientists would need to develop a new vaccine. However, if the pandemic strain is similar but not a perfect match to the vaccine strain, the vaccine may still be useful; studies have shown that influenza vaccine may provide some immunity against strains that are somewhat different.
What is avian influenza?
Avian influenza is caused by influenza A viruses that occur naturally among birds. There are different subtypes of these viruses and all known subtypes of influenza A viruses can be found in birds. The H5N1 strain is currently the main cause of concern because of its potential to cause a pandemic. The H5N1 strain can infect birds, other animals, and people.
While there have been no reported human cases of H5N1 infection in the United States, almost 300 people worldwide have been infected with this virus since 2003 and more than half of them have died. Right now, there is no influenza pandemic, but each illness in humans gives the virus an opportunity to improve its ability to spread from human to human and develop into a pandemic strain.
Who is the vaccine for?
The vaccine is intended for immunizing people 18 through 64 years of age who could be at increased risk of exposure to the H5N1 influenza virus contained in the vaccine. The vaccine immunization consists of two injections given in the upper arm muscle about one month apart.
Can I get vaccinated now?
No. The manufacturer, sanofi pasteur Inc. of Swiftwater, Pa., will not sell the vaccine commercially, meaning that you won't be able to get vaccinated against avian influenza in your doctor's office.
The federal government has purchased the vaccine to include within the U.S. Strategic National Stockpile for distribution by public health officials if needed. The stockpile contains large quantities of medicine and medical supplies to protect the American public if there is a public health emergency. These medicines and supplies can be delivered to any state in the United States within 12 hours.
To date, the U.S. Department of Health and Human Services has purchased 13 million doses of the avian influenza vaccine for the stockpile, enough to cover 6.5 million people.
How well does the vaccine work?
Of the 103 participants who received the vaccine in a clinical trial of healthy adults, 45 percent developed antibodies at a level that is expected to reduce the risk of getting H5N1 influenza. Although the remaining participants did not develop this level of antibodies, current scientific information on other influenza vaccines suggests that less than optimal antibody levels may still help reduce the severity of the disease and related hospitalizations and deaths.
Additional information on the H5N1 influenza vaccine is being collected on its safety and effectiveness in other age groups.
What are the most common side effects?
The most common side effects reported in the study were pain and tenderness at the injection site, headache, a general ill feeling, and muscle pain.
The manufacturer has agreed to work with the U.S. Government to gather more information on the safety and effectiveness of the vaccine if it is used in a pandemic.
For more information, visit www.fda.gov/oc/op/pandemic/default.htm
Date Posted: April 30, 2007
