New and Old Ways to Make Flu Vaccines by Nell Greenfieldboyce, NPR:

Standard Practice
Pros: Millions of Americans receive this [standard] vaccine every year. It’s safe and well tolerated. Its production begins in hens’ eggs — a tried and true technology for 50 years.
Cons: Eggs must be ordered many months in advance, and millions of doses require millions of 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.
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.
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.

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