Eggs Vital to Vaccine Manufacture

By Rachel Stockton

Have you ever wondered why healthcare providers ask you if you’re allergic to eggs before they give you a flu vaccine?  It’s because the virus is grown in fertilized eggs with embryos.  For whatever reason, the flu virus proliferates well in that environment.

According to the Chicago Tribune, the “seeds” of this year’s vaccine started in a laboratory housed at New York University.  The process is the same every year; researchers take a flu virus (in this case, of course, that virus was H1N1) then mutate it with another flu virus that is known to grow robustly in eggs.

This year was no different; the New York lab was able to get the “seeds” ready in short shrift before they sent them on to the manufacturers.  The request from health authorities was for 250 million vaccines.

Once the manufacturers got them, however, they found that the seeds grew more slowly, causing the current shortage of the vaccine we’ve been experiencing.  Researchers know that the virus is unpredictable, especially when you factor in the egg embryos.  To top it off, the swine flu is much slower than other, seasonal flu viruses.

However, the shortage isn’t just due to the slow growth process; some believe the Centers for Disease Control and Prevention was too optimistic to begin with.  It promised that there would be 120 million doses sent out to the public by mid-October. The actual number of vaccines that made it out of the lab is much lower than that rosy projection:  32 million doses have been released, thus far.

There is another way to grow viruses, experts say, but it’s very expensive.  The US Health and Human Services Department has given vaccine makers over $1 billion in funding to build sites that will facilitate the new method.  Perhaps the stall we’re experiencing with the H1N1 vaccine will motivate vaccine makers to press forward with construction.