NPR News

Comparing Flu Vaccines

NPR

Published November 7, 2007 at 6:09 PM EST

Flu vaccines provide protection against the influenza virus by presenting the human body with something that looks like the flu virus but that does not cause disease. Our immune systems recognize this material and produce antibodies to it. If we are exposed to an actual flu virus, those antibodies will neutralize the virus and protect us.

Below, a look at the pros and cons of various vaccine production methods, either being used today or in development:

STANDARD VACCINE

Pros:

Millions of Americans receive this vaccine every year. It's safe and well tolerated. Its production begins in hens' eggs — a tried and true technology for 50 years.

Cons:

The production method requires a great deal of planning. Eggs must be ordered many months in advance, and millions of doses require millions of eggs. Also, egg-based production could be problematic for a pandemic strain of flu that develops from a bird virus. That bird virus could be deadly to the chickens needed to make eggs.

LIVE-ATTENUATED VACCINE

Pros:

This newer method of production results in a vaccine that has a flu virus that is crippled, so it can't cause disease. But the virus is not killed, as is the case in the standard vaccine. The vaccine also can be given as a nasal spray (FluMist is the brand name).

Cons:

More expensive than standard vaccine, and also produced in eggs. Not approved for young children or older people.

CELL-BASED VACCINE

Pros:

This vaccine can be produced in giant vats of living cells. Such a production method means it can be scaled up much faster than egg-based vaccines, making it more useful in a pandemic. Several versions have been tested successfully in people. Earlier this year, the European Union approved a seasonal flu vaccine grown in cell culture. It's called Optaflu and is manufactured by Novartis, which is building a manufacturing facility in North Carolina that will produce cell-based flu vaccines.

Cons: Won't be widely available for a few years. Clinical trials are under way, but no flu vaccine made this way is currently approved by the Food and Drug Administration.

DNA VACCINE

Pros: Instead of injecting flu virus proteins into people, this concept involves injecting just the DNA from a flu virus. Human cells then "read" this DNA and create proteins that act as a vaccine. Manufacture of DNA could be much faster than that of conventional vaccines.

Cons: The method is being tested in human clinical trials, but development could still take years, and it may not prove to be safe and effective.

UNIVERSAL VACCINE

Pros:

Scientists would like to develop a flu vaccine that can be given just once and last for life, as is the case for some childhood vaccines. Current vaccines have to be tailored to protect against specific strains of flu viruses. This one, ideally, would protect against them all.

Cons:

This is currently more a concept than an actual product, though scientists do have some strategies that could ultimately lead to a universal vaccine.

-- By Richard Harris and Nell Greenfieldboyce