Influenza Vaccines and Drugs

by Food and Drug Administration (FDA)

(Page 3 of 3)

New vaccines and faster production

Scientists and public health experts are looking for ways to boost the production of influenza vaccine and make it available more quickly to more people. And researchers are looking at new technologies that could be used to produce vaccine, not just for seasonal influenza, but for a pandemic-a worldwide outbreak of serious illness.

One of the technologies researchers are using is cell culture production, which allows a virus to grow and multiply in living animal cells instead of eggs. Cell-based vaccines could help meet surge capacity-making a lot of vaccine in a short time period-in the event of a shortage or a pandemic.

With cell culture production, cells can be frozen and stored, and then thawed out and used to produce more vaccine as needed-a speedier process than acquiring millions more fertilized eggs. Like the current method of influenza vaccine production, the safety of vaccines produced in cell culture would be thoroughly evaluated by the FDA.

In May 2006, Health and Human Services Secretary Mike Leavitt announced the department's investment of more than $1 billion in contracts with five companies to develop influenza vaccine made from cell culture.

Researchers also are looking at recombinant vaccines, made by genetic engineering, for influenza prevention. The gene from a specific influenza protein is isolated from the influenza virus, cloned, and grown in yeast or other cells to create large amounts of the protein. The protein produced is purified and then used to make vaccine. When the vaccine is injected into a person, the body's immune response to the recombinant protein protects against infection by the naturally occurring virus.

Researchers also are experimenting with substances that enhance vaccine effectiveness (adjuvants) to make current vaccines more potent. "If you could double the potency, the current technology could make twice as many doses, which would make 50 percent of the doses available sooner," says George Curlin, M.D., M.P.H., an infectious diseases researcher and adviser on vaccine clinical trials at the National Institute of Allergy and Infectious Diseases. Studies supported by the NIH are under way using adjuvants as a "dose-sparing" technology.

Another area of research is a universal vaccine. This one-shot-fits-all vaccine would protect people for years against all strains of influenza anywhere in the world. Although universal vaccine research has been going on for decades, says Curlin, "nothing seems like it's available right around the corner, but there are clinical trials starting."

The FDA stimulates vaccine development

The FDA has worked to streamline the vaccine approval and licensing process to encourage new vaccine development and to make vaccines available for use sooner. In March 2006, the agency published recommendations, in the form of two draft guidelines, to aid manufacturers in developing vaccines for both seasonal and pandemic influenza. The guidelines give specific approaches that vaccine developers can follow to show the safety and effectiveness of new vaccines, and they provide flexible, regulatory pathways for getting vaccines on the market.

One of these pathways is the accelerated approval process, which can reduce the development time for a new vaccine. For an application that does not use the accelerated approval pathway, a company must show that a vaccine actually prevents influenza, which requires waiting to see whether people in studies get sick or not. For accelerated approval, if the manufacturer demonstrates that within weeks after vaccination, adequate levels of protective antibodies are made in the blood that the FDA believes may prevent influenza, then this approach may be acceptable. If the accelerated approval approach is used, further studies are required after approval to make sure that the vaccine actually prevents influenza.

The accelerated approval pathway was critical in allowing the rapid approval in 2005 of Fluarix, a new influenza vaccine and the first vaccine of any kind approved using the FDA's accelerated approval process.

The FDA has corresponded with the major manufacturers of influenza vaccine in the world to stimulate interest in producing vaccine for the U.S. market. This outreach resulted in one additional vaccine product approval for the 2005-2006 season, and the possibility for others in future influenza seasons.

The FDA is also undertaking efforts to aid development of influenza vaccines using new technologies. To accomplish this goal, the CBER is using various approaches to reach a broad audience, such as convening an advisory committee meeting to discuss the use of novel cell substrates for making influenza vaccine, and having frequent interactions with vaccine manufacturers to provide both scientific and regulatory guidance. In addition, the CBER is participating in and leading meetings with industry, regulatory authorities of other nations, and stakeholders concerning the development of influenza vaccine.

Drugs to prevent or treat influenza

Getting an annual influenza vaccination continues to be the first line of defense against seasonal influenza. But antiviral drugs-started within the first two days of experiencing influenza symptoms-can shorten the time influenza lasts.

The FDA has approved four antiviral prescription drugs to treat influenza: Tamiflu (oseltamivir), Relenza (zanamivir), Symmetrel and generics (amantadine), and Flumadine and generics (rimantadine).

All of these drugs also are approved to prevent influenza, but they are not substitutes for influenza vaccine. The CDC recommends that the drugs be used in specific circumstances, for example, in combination with the vaccine to help control influenza outbreaks in institutions such as nursing homes where people at high risk for complications from influenza are in close contact with each other. The antiviral drugs should not be used, however, in people who receive inhaled influenza vaccine until at least two weeks after vaccination. In addition, people should not get vaccinated within two days of stopping the use of antiviral drugs.

The drugs may be prescribed by a doctor to prevent influenza in place of vaccine in certain people, such as those who are allergic to eggs, the medium used to grow the virus for the vaccine.

Influenza viruses can rapidly develop resistance to certain drugs. Because of recent evidence that many circulating influenza viruses are resistant to amantadine and rimantadine, the CDC has recommended that these drugs not be used to treat or prevent influenza in the United States at this time.

DTips to help prevent influenza

The Centers for Disease Control and Prevention recommends the following good health habits to help prevent getting influenza:

• Avoid close contact.Keep your distance from people who are sick.
• Stay home from work, school, and errands, if possible, when you are sick.
• Use a tissue to cover your mouth and nosewhen coughing or sneezing.
• Wash your hands frequently with warm, soapy water for about 15 seconds to help protect you from germs.
• Avoid touching your eyes, nose, or mouth.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.