Eggs & Flu Vaccines

Living and learning...
Did you know that all flu vaccines are made using eggs?
Well, they are. Even the nasal spray mist vaccine (FluMist), introduced in 2003, uses them in the production process. Other inoculations, such as the polio vaccine, are produced using cell cultures, but these methods have been adapted for influenza.

Flu vaccines are cultured by making a tiny hole through the egg shell of a chicken egg. The influenza virus is injected, infecting the chick embryo and the surrounding fluid. Several days later, the egg is opened. Its contents are extracted and treated to kill the virus. To make sure the virus is dead, a portion of the liquid is implanted in another egg, which is tested for any sign of virus replication.
On average, one or two eggs are required per immunization, and the production process uses nearly 100 million eggs per year. Needles to say, intensive egg laying operations have raised serious animal welfare issues.

The method has scientific drawbacks, too. First because the production process is slow, scientists must decide months in advance which virus are likely to circulate the following winter. If they are wrong, the vaccine will be less effective. Second, because the vaccine may contain traces of egg protein, people with egg allergies can react to the vaccine as they would to eating eggs.

[source: Neal Barnard, MD, interview to Vegetarian Times]